Solar PV panels have reduced in price by approximately 40% as a result of falling manufacturing costs and increased competition in the market. This means you can now get a decent sized solar PV system installed on your roof for between £4,000 and £6,000.
We would always recommend trying to maximise the number of solar panels that you go for – but this is often limited by the size of the roof space.
A 250w solar panel will typically cost between £300 and £500 and each panel is approximately 1.7m2. Therefore for a 3.5kW system, you are looking at a price of between £4,200 and £7,000, and this would take up approximately 23.8m2.
For a smaller 2.0kW system, you are looking at paying between £2,400 and £4,000 and this size system would take up approximately 13.6m2.
Obviously, the more solar panels you have on the roof, the more electricity you can produce. This therefore means you need to buy less electricity from the grid (as you can use the electricity you produce).
You can also get payment from your energy supplier, provided they are signed up to the Smart Export Guarantee (SEG).
The SEG is a legal obligation for any electricity supplier that supplies at least 150,000 customers to offer an export tariff to those with solar panels for each kWh produced.
The actual export tariffs these energy companies offer can be flat, variable or smart rate (adjusting based on wholesale prices), however the tariff must always be greater than zero (even when wholesale prices of electricity are negative).
There is quite a large discrepancy between the different SEG rates from the different providers – for example in August 2020, Utility Warehouse offer £0.02 / kWh, while Octopus are offering £0.055 / kWh.
SEG versus FIT
The SEG was introduced in January 2020 to replace the older Feed in Tariff (FIT) scheme, which closed to new customers on 31st March 2019.
The main difference between SEG and the FIT scheme was that the FIT scheme paid the owner of the solar panels for both producing the electricity and also for exporting it, while the SEG only pays for exporting it – therefore the SEG is far less generous.
Eligibility for the SEG
To be eligible for the SEG, the solar system being installed needs to be under 5MW (or approximately 20,000 solar panels – so most homes should be okay!). The solar system must also be installed by an MSC certified installer. Finally you need to have a smart export meter installed to measure how much of the electricity is being exported back to the grid.
SEG Tariff vs. using the electricity at home
To maximise the return from the solar PV installation, you will want to use as much of the electricity you produce in your home as possible. In the most basic terms, if you use the electricity you produce in the home, then you don’t need to buy it from your energy provider (a saving of around 15p/kWh). If you export it, you only get paid a fraction of this (£0.05 at most!) – so if you can use it in the home, then it is strongly recommended to use it!
By incorporating battery storage technology into your solar system setup – it allows you to store the electricity you produce to use as and when you need it. You can learn more about battery technology by clicking here.
Solar PV worked examples
So, to start with, we will look at a typical 3kWh system (installed on a new build with a ‘higher’ energy efficiency requirement rating) and see the annual return, based on the percentage you use in the home versus how much you export. Over a year, a 3kW system would expect to be around 90% efficient and generate about 2700 kWh of electricity (an average home used 4,800 kWh per year).
Worked Examples – % of Electricity used in the Home : % of Electricity Exported to the Grid
100% : 0%
75% : 25%
50% : 50%
25% : 75%
Used by household (£0.15/kWh)
These numbers are correct as of 18th August 2020.
What impacts the initial cost of your solar PV installation?
The cost of your solar PV system is dependent on two things:
1. The size of the installation
Obviously the larger the system you install, the more electricity it has the potential to produce. The average solar PV system installed in the UK now is 3.5KW, which – working at 90% efficiency – will produce approximately 3150kWh of electricity (depending how much sun you get in your part of the country). As reference, an average house uses approximately 4,800kWh. The number of panels you can install will probably be limited by either the amount you can afford or the size of your roof. Suppliers will also charge different prices for their installation services and it’s important to ensure they are MCS-accredited to qualify for the SEG
2. The quality of the solar panels used
Not all solar panels are the same!
See our guide to the different types of solar panels for more details, but in a nutshell there are three types:
Monocrystalline solar cells (made from single crystals grown in isolation) are the most efficient at 15-22%, but they are also the most expensive type of solar cell.
Polycrystalline cells are cheaper than monocrystalline, but their efficiency is far lower at just 13-17%.
The cheapest solar cells of all are amorphous solar cells, which also have the bonus of being more efficient in low-light (great if you live in the UK!) but they are the least efficient overall at 9%.
How are the efficiency figures calculated? Well it is determined by how many watts of power are produced in a square meter. 100% efficiency means that a square meter of panel would create 1,000 watts. Therefore a panel rated at 18% would create 180 watts from every m2; it follows that panels with higher efficiency ratings create more electricity (per meter squared) and this is reflected in the price.
As you can see in the table above, the actual price of your installation varies depending on the types of panel you get installed, so a 4kW system could cost as little as £4,800, or as much as £8,000. In the table below we have assumed we are exporting 50% (so this is eligible for the SEG) and 50% is used within the home (so a saving on the electricity bill).
Type of Panel
Efficiency of Panel
Savings on electricity bill (£)
Annual Return (£)
Payback of your Solar System
So looking at ‘System A’ in the table above, the system costs £4,800 and the annual return is £320 per year, so it will take approximately 15 years to pay back. In addition, electricity prices are expected to go up over time, so the £0.15 you save for every kWh of electricity you use in your home will actually increase – and could be nearer 20 pence in just 5 years – therefore the absolute return could actually become bigger.
Once you have ‘made your money back’, then any money you make is paid directly to you as profit – so you will be in line to receive the SEG indefinitely while you are exporting electricity.
There are a few other costs to think about with solar PV
There are maintenance costs associated with your solar PV installation, including cleaning them at least twice a year to ensure they are working as efficiently as they can.
In addition, despite the solar panels being good for 20 years plus, the inverters have a lifespan of about 10 years, and replacing these will cost just shy of £1,000 – so factor this in to your calculations when your solar installers give you a quote.
You will need to insure you solar PV array as part of your home insurance, so your insurance premium payments will slightly increase.
Installing solar panels on your roof does normally not require planning permission. However if you live in a conservation area or world heritage site, you will need to speak to your planning authority to get the necessary permission. Note: there will also be legal fees associated with this.
Installing Solar PV
Are you thinking about installing a solar PV system at home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer to help install a solar PV system in your home, just fill in the form below and we will be in touch shortly!
Windmills (now in the form of wind turbines) have been used for millennia to convert the wind’s kinetic energy into mechanical energy. As early as 200 B.C., mechanical energy was used for specific tasks including grinding grain and pumping water. Nowadays, wind turbines harness kinetic energy from the air and convert it into electricity via a generator.
Much like solar PV installations, you can purchase a domestic wind turbine to supply as much or as little electricity as you want. If you are hoping to limit your dependence on the mains as much as possible, you will need a larger turbine, or multiple smaller turbines. If you are simply looking to produce enough electricity for a light in your garden shed, you can get away with a very small turbine.
Below we look at the different types of wind turbine system you can install in your property.
Battery-less grid tied systems
Battery-less grid tied systems are the simplest, most effective and most environmentally-friendly wind turbine systems. Their role is simple: to produce the most electricity possible to provide electricity for your home and also feed into the grid. Due to the availability of grants such as the feed-in tariffs in the UK, this type of system has grown enormously in popularity in recent years. In these installations, the home owner can effectively sell the surplus energy back to the utility company. There are no batteries in the system, so this removes a lot of the system complication and maintenance. The lack of batteries also makes it cheaper to install.
If your aim is to become completely unreliant on the grid, then you need to ensure the electricity produced by your battery-less grid tied system is in excess of your total electricity usage for the year. However, this system should suit most budgets, because it will reduce reliance on the energy companies, by significantly reducing your bills. If you cannot produce all your electricity, the shortfall is simply made up with electricity from the grid.
There is one major drawback with this setup, and that is that if there is a electrical power cut then you will have no power for your home, because the inverter your energy goes through is connected to mains power, so you may require a generator (powered by diesel or oil) as a back-up policy.
Grid-tied system with battery backup
This is essentially the same as the grid-tied system above, but has a bank of batteries which means that if there is a grid power cut, the inverter can still get the electricity it requires to operate, so the installation will keep providing you with electricity. The constraints of this system are primarily associated with the batteries, which are expensive and require regular maintenance. Finally, add extra inefficiency into the system (ranging from 5 – 40%) and this is added to the constraint side.
This system has no connection at all to the grid, relying instead on batteries to operate if no wind is blowing. However if the capacity of these batteries is too low, then you could be without any power for a prolonged period of time. Having a system off-grid presents an ideal situation as you become completely independent from the grid, and you produce all the electricity you need. However, this type of system tends to be the most expensive and also is maintenance-heavy. If you have a garden shed that needs lighting then this system can work out relatively cheaply, but as soon as you are looking to upscale then it becomes very expensive.
In the next section we look at the components that you need for a successful wind turbine installation.
Wind turbines allow you to produce 100% clean, free electricity.
Wind turbines can be considered a bit of an eyesore and often have to be limited to rural areas.
Entirely dependent on the size of the wind turbine, from £1k – £10k.
Solar prices are crashing – great for consumers!
June 26, 2013
Solar Prices are Getting Cheaper
In a world that seems to be getting more expensive on a daily basis it is refreshing to read that one of the great hopes for our future energy security is significantly reducing in price across the globe.
The following graph shows the price of crystalline silicon photovoltaic cells when they came onto the market in 1977 and how the price has decreased over ever since.
The rule of thumb for this decrease is that the cost to generate the photovoltaic cells falls by 20% with each doubling of global manufacturing capability.
Solar – A maturing market
The solar industry is a funny one, since only a few years ago installing solar panels on your roof was seen as somewhat of a luxury because they were prohibitively expensive and the financial payback was 15 – 20 years or more.
Then all of a sudden, the Chinese Government invested heavily in solar via the Chinese Development Bank, which provided very cheap debt to solar manufacturers as well as tax breaks and subsidies. In 2010 alone, $30bn was handed out to 5 solar companies in China, allowing them to expand their operations very rapidly, leading to a much higher manufacturing capacity.
This move by the Chinese effectively turned the whole industry on its head, but quickly resulted in supply vastly outstripping demand, resulting in solar cell prices tanking.
Now obviously this isn’t good news for the big solar manufacturing companies outside of China who are looking to make profits from the goods they are selling. Only a few weeks ago, Suntech, one of the world’s biggest solar panel manufacturers, defaulted on a $500m bond payment.
In fact, in an effort to slow the massive influx of Chinese manufactured solar panels, the EU has imposed anti-dumping duties on Chinese solar imports having found that they were selling them in Europe at 88% lower than cost. This tax import rate is currently set by the EU at 11.8%, however if China refuse to stop their solar panel dumping the rate will go up to 47.6% in August.
This unfortunately has created an issue for many UK based installers who get their panels directly from China, since they will no longer be able to import them so cheaply; a situation that could mark the end of the cheap home solar PV installation
The Tanking solar Price is (currently) great for Consumers
Thus far, this fierce competition introduced by the influx of new Chinese solar companies has been great for consumers (driving down prices of solar panels), but if UK installers need to start paying almost 50% tax on the panels they import then their prices will need to increase accordingly.
It is currently possible to buy a 4kW system in the UK for approximately £7,000 – £8,000. A system this size should produce about 3,400kWh of electricity per year. If you were to use half of this yourself and sell half back to the grid you would make approximately £850 per year as per the calculations below.
Cash to you
Generating Tariff (part of FiT)
Export Tariff (assumed 50%)
Saving on electricity bill
Therefore the payback is less than 9 years, and then you will continue receiving the subsidies for the next 10/11 years (20 years after installation).
This is obviously the situation as it is today, but this could change in a matter of weeks – so act quickly to ensure you get the best deal on your solar panels. The Feed in tariff is also reviewed on a quarterly basis, so is likely to continue to fall over the coming years, so now is the perfect time to install a solar system.
Looking Forward to the Future
Despite the issues surrounding the cost of the panels resulting from the sudden increase in Chinese manufacturing capacity and the EUs decision to tax panels made there, the technology that goes into making the panels is improving on a seemingly daily basis.
Even last week, the Stanford Institute for Materials and Energy Sciences announced massive efficiency improvements (about a 100 fold increase) on a solar cell that can convert all solar wavelengths into electricity (current PV only uses the visible spectrum). Where heat negatively impacts traditional solar PV cells, this new technology performs substantially better in warm conditions.
I have written before that it will be a big day for solar when installed it can produce electricity at the same price as traditional fossil fuels (which is almost the case in California now) – known as grid parity. And hopefully one doesn’t have to look too far into the future to a time when grid parity could be reached in sunny UK too, there just might be a few speedbumps along the way!
Microgeneration Certification Scheme (MCS)
What exactly is the Microgeneration Certification Scheme?
You will see across the site that we recommend installing microgeneration products that have the MCS stamp of approval. This is an eligibility requirement both for the Government Feed-in Tariff (FiTs) and the Renewable Heat Incentive (RHI – launching in Spring 2014), but what actually is it?
MCS stands for Microgeneration Certification Scheme and this is an internationally recognised quality assurance scheme fully supported by the Department of Energy and Climate Change. The MCS certifies products that produce electricity and heat from renewable resources.
It ensures that any microgeneration or renewable products you install (e.g. solar PV) have gone through a comprehensive assessment ensuring that they are built to a sufficient quality, they perform at an optimal level and they operate safely.
The MCS allows consumers to easily recognise good quality products and be sure that the performance promised by the manufacturer is what you might expect in reality.
MCS certifies electricity generating products up to 50 kW, CHP products up to 50kW and renewable heating products of up to 45kW.
MCS also covers Installers
Apart from using products that have the MCS stamp of approval, you also need to ensure that MCS approved installers have installed them. Making sure you use installers that are MCS qualified will help ensure you receive the money you are entitled to under the Feed-in Tarff, the Renewable Heat Premium Payment and any of the other renewable energy grants.
What Microgeneration products fall under the MCS?
The following renewable products fall under MCS quality assurance mechanism:
At present, the only other scheme that can be considered equivalent to the MCS is the CEN Solar Keymark Scheme, however this only covers solar heating collectors and it does not cover their installation (e.g. you will need to get the product installed by a MCS certified installer to ensure you are eligible for Government grants and subsidies).
How do I find an MCS accredited Installer
Before you begin your search to find an MCS accredited installer, make sure you understand everything you need to know about the renewable technology that you are trying to install. For ideas on renewable solutions please see our self generation section.
When you have acquired the knowledge in the technology, it is the right time to find an MCS approved supplier. If you go onto the Microgeneration Certification search functionality and find yourself 3 installers. It is important to get quotes so you get the best price for your work.
You will then get the products installed by the MCS approved installer. Once this is complete you should then receive your MCS approved certificate. If you click on the Feed-in Tariff page you will see what you need to do to start claiming your FiT payments.
Micro Hydroelectric Power
Hydroelectric power on a residential scale
It is well known that energy is generated by building dams over giant underwater turbines; however it is possible to use micro hydro generators (<100kW) or pico hydro generators (<5kW) on more modest water flows. In this section we explore where the technology can be used in a small scale area, for example the home or a community project. More about industrial size dams and solutions can be found in the green commercial section.
Obviously, there is a fundamental requirement on a steady stream of moving water, however they have an advantage over solar power (both solar PV and solar heating) and wind, in that they can run day and night and in any weather conditions provided the we don’t have a prolonged drought period where streams and brooks can dry up.
The amount of energy produced is reliant on two things:
The flow of water
The flow of water is simply the quantity of water flowing in the water source, which is measured in litres per second.
The other key factor is the head – this refers to the pressure at which the water hits the turbine blades, and is the vertical distance from the water source to the generator. The larger the distance that the water falls before it hits the blade, the higher the head. Ideally both the flow and the head will be high, however if one of these is particularly high, while the other is low there is still the potential for a rich source of electricity.
You can estimate the number of kilowatts of energy produced by multiplying the flow (litres/sec) by the head (m) and multiplying by 9.81 (gravitational constant). Remember a typical house uses 4500kWh per year.
The type of turbine that is used varies depending on the type of flow available, however typically a residential generator uses a pipe to collect water from a river or a stream. Using gravity the water moves through the pipe ‘downhill’ and a generator situated within the pipe acts to change the kinetic energy from the water flow into electrical energy.
When you have high head (the vertical distance from the water source to the generator), you are best using an impulse turbine (such as a Pelton turbine). This turbine is not submerged in the water, instead it sits in the air, and consists of buckets around a central hub. The nozzle at the end of the pipe converts the water into a fast moving jet. This jet of water is directed at the buckets, and the force of the the water causes the turbine to spin generating the power. The smallest type of high head turbine requires a head of at least 10-14 metres, and a water flow of 3-4 litres/ second, and this is rated at producing 200 watts of power.
For medium head water flows, it is best to use a reaction turbine. With a 3-12 metre head and a water flow of 45 litres/ second, you can get a reaction turbine that will produce about 3000 watts of power. Obviously as with the high head turbines, if either the head or the flow increases, you will see dramatic increases in the potential electricity your system is capable of generating.
For low head water flows, you obviously require a high flow rate, and in this situation an old style water wheel is the best. So the water fills the buckets which fill up, then pulling the wheel down, so the next bucket is filled, and this process is continued so the wheel spins (albeit very slowly). However the advantage of this type of system is that any potential blockages just simply wash through the system. Gearing can be used in conjunction with water wheels to increase the speed that the generator spins to help electricity production. Water wheels are also aesthetically pleasing on the eye!
Summary of micro hydroelectric power
If you are lucky enough to have a water flow source on your property that either has high head or sizeable flow, a micro hydroelectric generating system may be the perfect solution for your energy needs. Despite potential seasonal fluctuations in flow and head, a micro hydroelectric system will provide you with electricity 24/7, with very little maintenance necessary.
To maximise the electricity contribution that a wind turbine can provide you with, two interlinked questions need to be considered:
How much electricity you would like to produce?
How much electricity you can produce on your property?
How much electricity do you need your turbine to produce?
You first you need to decide exactly what you are trying to achieve by installing a wind turbine on your property. Are you trying to become completely independent from the grid? Are you simply trying to decrease you electricity bills having received a capital lump sum that you can invest? Do you simply want a wind turbine to power a light in your garden shed? Obviously the larger the turbine, the more electricity it will produce; however larger turbines will be more costly.
By looking at utility bills from previous quarters, you can get a feel for your total electricity usage over a year. You can get more accurate readings if you go around your property and complete an energy assessment of your current load (simply the total energy that each appliance in your house uses over a certain period of time). This involves producing a table with each appliance, its draw in watts (measured using a watt plug in meter – sometimes known as a wattmeter), and the estimated time of use in a 24 hour cycle. With all this information you can complete a much more accurate total yearly assessment of usage of your house (by multiplying usage for a 24 hour cycle by 365 days).
Having a feel for your total energy usage should help you decide what you are trying to achieve with your turbine. There are several wind turbine setups which we have described in more detail below.
How much electricity can your system produce?
It is really important that you have a target electricity figure in your mind that you are aiming to achieve, be it 50% of your total energy requirements, or becoming fully self sufficient. However, this may not be possible if there are constraints on your property, such as lack of space or low average wind speed.
This is the key factor and we usually use average wind speed as the measurement for your particular location. You cannot directly affect the average wind speed at your home; however your choice of site and tower height can have a dramatic impact on the wind resource. The power available for the wind that is blowing is the cube of the wind speed – this is absolutely fundamental, and this can be seen in the simple sums below:
3mph – 3 x 3 x 3 = 27kWh
6mph – 6 x 6 x 6 = 216kWh
12mph – 12 x 12 x 12 = 1,728kWh
This is excellent news, as the further you get away from the surface of the earth and its many obstructions (e.g. houses), the higher the wind speed: therefore the more power in the wind. This means it is important to try and maximise the height of any tower you use, to try to maximise the wind potential of your wind turbine system.
The swept area is the circle that the turbine produces when spinning, so this is the diameter of the blades. The blades are driven by the power in the wind, so the larger your swept area, the more energy you can harness. Again the easiest way to illustrate this is with some more simple sums (apologies for those adverse to maths!), where the area of a circle is half the diameter2 x π. (π = 3.14)
3 foot diameter = 1.5 x 1.5 x 3.14 = 7ft2
6 foot diameter = 3 x 3 x 3.14 = 28ft2
12 foot diameter = 6 x 6 x 3.14 = 113ft2
Taking into account these two factors, you can see the maximum electricity you can produce. Remember that wind speed is free (although towers obviously cost more money the higher they are), while investing in bigger and bigger turbines gets more expensive.
What size turbine should you be looking at?
The size of your wind turbine is therefore determined by the amount of electricity you are looking to produce (but potentially constrained by windspeed and space), and secondly the amount of cash you have available.
Unlike solar photovoltaic cells that can be added to fairly easily as additional funds become available, the turbine blades would need to be replaced, and potentially the generator changed if you want to produce more power in the future. Home scale generators normally are between 8 and 25 feet in diameter (so a swept area of between 50 – 500 feet2). If you have an average wind speed of 10 mph, these could produce between 1,000 and 15,000 kWh. An average house uses approximately 4,800 kWh per year, so a 25 foot diameter turbine is going to produce a serious excess of power to sell back to the grid, or power more than one house.
Final thoughts on wind turbines
Contact your local council to ask about planning permission if you’re considering installing a wind turbine. The majority of local authorities are keen to encourage the installation of renewable energy systems. However it is a good idea to consult your neighbours before investing time and money into the planning phase, to allow them to voice any objections.
Average wind speed
Before you even consider investing in a wind turbine, you need to check your average wind speed. The Carbon Trust have created a tool that allows you to estimate the wind yield at your home location. You are looking for an average wind speed in excess of 5m/s. By providing simple information regarding your location and type of turbine, the tool will give you average wind speed and potential energy output.
In the UK, as a wind turbine owner you can benefit from the Feed-in tariffs. There are different allowances depending on the power output of your equipment. Wind turbines above 5MW are classified as commercial and alternatively benefit from the Renewable Obligation Certificates. The Feed-in tariffs basically provide you with a source of income for every kWh of electricity you produce. This is independent from any excess electricity you sell back to the grid, which you further benefit from in the form of the export tariff. This can really help a wind turbine become an economically viable system to put into your house.
What is Hydroelectric Power?
Hydroelectric power is a very well established form of providing energy. In the last decade, 20% of the world’s electricity came from hydroelectric plants (88% of the renewable energy supply). This balance will change as there are now competing renewable energy generating sources like solar PV, and wind power. Hydroelectric power means harnessing power from moving water using an electric generator. In the UK, total hydroelectric power capacity is just under 2%, which makes up under a fifth of the total renewable energy generation capacity. When people around the world think about hydroelectric power, they probably think of the Hoover Dam, which is located on the Colorado River in the USA, between Arizona and Nevada. It was completed in 1936 and had a maximum generating capacity of 1.3GW.
How does Hydroelectric Power Work?
Power is generated as massive turbines spin, which is caused by water flowing over them. When the turbines spin the magnets in the generator, this causes a conversion of kinetic energy to electrical energy. The amount of power generated varies depending on the volume of water that passes over the turbines and the difference in height between the water source and the water’s outflow (known as the head). There are different bands of hydroelectric power plant, divided by the amount of energy they can produce. The power plant divides are as follows – large (few hundred MWs to 10GW), small (up to 10MW), micro (up to 100KW) and pico (under 5KW).
One of the major advantages of hydroelectric power is that it can be harnessed within seconds depending on demand, and as such is one of the only means of storing large quantities of electrical energy for peak demand. This is achieved by holding large amounts of water in a reservoir behind a dam with a hydroelectric power plant below. For example Dinorwig, in Wales can help provide emergency power to fill the demand gaps from a city such as Liverpool. Most power stations, including fossil fuel and nuclear have to stay on at all times as they take time to warm up to produce the power, and cool down for maintenance. As a result, these are used to service base demand, then hydroelectric power can service any spikes in demand, and then water can be pumped back up into the reservoirs when demand is less (during the night).
Types of Hydroelectric Power
Hydroelectric Power Dam Storage
This is the conventional hydroelectric power station most people refer to when discussing hydroelectric power. It involves building a dam across a river, which traps the water creating a large artificial lake or reservoir behind it. To create electricity, gates are opened at the bottom of the dam and gravity pushes the water through the gates and down a pipe known as penstock, which delivers the water directly to the turbines built into the structure of the dam. This fast flowing water turns the turbines, and the generator system converts this kinetic energy into electrical energy. An example of a hydroelectric power dam, is the Kielder Water reservoir, located in Northumberland, operated by RWE Npower and is the largest system in England.
Hydroelectric Power Pumped Storage
Pumped storage hydroelectric power, as described in the Energy Storage section requires two reservoirs, one at high altitude and one at low altitude. When the water is released from the high altitude reservoir, energy is created by the downflow which is directed through high-pressure shafts, linked to turbines. This pressure drives the turbines which in turn power the generators that create the electricity. When the high altitude reservoir is empty, water is pumped back to it from the lower reservoir. This is linked with a pump shaft to the turbine shaft, using a motor to drive the pump.
In the UK, Dinorwig Hydroelectric Power plant uses pump motors that are powered from electricity from the grid, when the electricity is cheaper overnight, and demand is at its lowest. Hydroelectric power pumped storage generation therefore offers a critical back-up facility during periods of excessive demand, whilst being efficient in storing energy during periods of low demand.
Some hydroelectric power systems utilise the natural flow of a river to create electricity without needing to build a dam. These types of hydroelectric power station involve forcing the river flow through penstocks and turbines to create the electricity, but the structures that are put across the river are far smaller than used in the hydroelectric power dam storage described above.
In Beeston, Nottinghamshire, the hydroelectric power plant run by United Utilities is the largest run-of-the-river system in England. The difference between a dam and a run-of-the-river system is that the latter uses free flowing water, and has minimal storage capacity, which has its advantages and disadvantages. The system requires volume of water passing through and without storage capacity may lack the power of velocity. The dam and the river systems can both be example of diversion schemes, where they can both use water that is channelled from a river or a lake
Hydroelectric Power Industry Development
In the UK, the largest hydroelectric power station is at Dinorwig, which is capable of generating 1.8GW of power in just 12 seconds. However looking around the world, this is dwarfed by the largest hydroelectric power station, the Three Gorges Dam located in China. This hydroelectric power plant has a generating capacity of 20.3GW, which at the time was expected to service 10% of China’s electricity needs, however since their demand has increased so dramatically in recent times, it currently only services about 3%.
Hydroelectric power generators in the UK are eligible for Renewable Obligation Certificates (ROCs) with stations commissioned after 2002 that have 20MW of power output and for all that are below this level. According to the DECC, there is no national strategy for nationwide development of hydroelectric power, but the government is committed to do everything in its power to support developers, community initiatives and small scale developers being able to invest and build hydro projects. In addition, schemes up to 50kW can only apply for FITs, whereas schemes between 50kW and 5MW can choose between FITs or ROCs.
What is Geothermal Power?
Geothermal power is utilising energy that comes in the form of heat from beneath the earth’s crust/ surface layer. Essentially this is utilising the same scientific principles as used in ground source heat pumps, but on an industrial scale. Geothermal power relies on large generators and infrastructure that can provide both heat and electricity to multiple dwellings and commercial properties.
Geothermal power is a renewable heat source that can provide energy for electricity production as well as heating for a number of applications and appliances. Currently in the UK there is one working geothermal power plant in Southampton, which is providing a local district heating solution rather than being used an electricity generating power plant.
Some areas of the world have much more geothermal activity (such as Iceland, West Coast of the US, Rotorua in New Zealand, etc.), and these are more obvious places to harness the earth’s geothermal power. However, if you dig deep enough, heat is available anywhere across the globe (including the UK) so we could definitely roll out this technology more, and build on expertise to harvest the heat in more effective ways.
The science behind geothermal power is relatively simple; heat is continuously flowing from the Earth’s core by conduction (travelling from hot to cold) to the surface and is therefore considered as renewable source as long as the Earth continues to have an active core. It is estimated that geothermal power could produce 44million MWs of power, so even if we could tap a very small percentage of this it would service most of our energy needs.
Geothermal Power for Electricity Generation
Utilising geothermal power requires accessing high temperature fluid that is heated deep underground. Historically this fluid has existed underground, formed by rainwater passing through cracks in the crust. The water is heated by hot rock underneath and compressed by pressure that maintain it its liquid form. The water potentially then finds a path through the Earth’s crust, and presents itself on the surface as hot water springs or geysers.
Nowadays, in addition to this naturally occurring phenomenon, we can also artificially mimic this by pumping cold surface water down into the earth’s crust, where it gets superheated and returns to the surface via circulation pumps. Existing Geothermal Power plants have either tapped into the naturally occurring process or mimicked this to produce the steam necessary to drive turbines to create electricity. As we can now have the technology to drill deeper than ever into the Earth’s crust, by utilising the man made process, we can implement geothermal power stations anywhere in the world.
Three common Geothermal Power generating systems
Dry Steam Geothermal Power
Dry steam geothermal power plants use geothermal steam directly to turn the electricity producing turbines. To have this structure in place requires steam directly travelling to the Earth’s surface, which is quite a rare phenomenon, so there are only few examples of this type of power station worldwide. The geothermal steam, which is superheated (above 1000C) is forced up through cracks in the ground under great pressure. The pressure of hot steam is driven through pipe shafts, which then rotate the turbines. The turbines drive a generator, which creates the electrical charge. Hot steam is then cooled in a cold heat exchanger and the cold water is then pumped back into the ground, which then kicks off this cycle again.
Flash System Geothermal Power
Flash steam geothermal power plants rely on highly pressurised, superheated water instead of steam. The highly pressurised liquid is pushed through a series of pressure tanks. In turn, these holding tanks reduce the pressure of the liquid, allowing it to turn into steam. This process is repeated several times in different depressurised chambers with the steam then collected and ’flashed’ through to drive a turbine generator system to create electricity. As with the dry steam geothermal power system, the excess hot liquid is cooled and / or condensed and then pumped back into the ground so the liquid is replenished.
Binary Cycle Geothermal Power
Binary cycle geothermal power plants use lower temperatures to produce energy and use technology much like that used in OTEC, using the heat gradient to turn a working fluid, such as ammonium and/ or propane into steam to drive the electro generating system. This type of system can be implemented using lower ground temperature as a working fluid has a lower boiling point than water. Once the working fluid passes through the turbine shafts, it is condensed back into the liquid and reused over and over again.
Geothermal Power for Heating
We have talked a lot about electricity generation in the above section, however geothermal power can also be used for heating solutions. Like ground source heat pump systems used in the home, a geothermal power system can be implemented as a district heating solution. In the UK, this would be optimal in areas that are not covered by the current gas grid. Using residual heat from the dry steam or flash system geothermal processes, local homes and businesses could be supplied with heat all year round.
The slight issue in the UK, is that the infrastructure requires investment by the generation companies to make this a feasible proposition, it would however allow them to supply both heat and power (CHP cogeneration) to consumers. These types of solutions are currently more common in Scandinavian countries, and therefore the UK is playing catch up as far as geothermal power goes.
Where is Geothermal Power now?
In the UK, there is enthusiasm about the prospects of geothermal power, but thus far DECC has not provided the additional support that the technology really needs to make a suitable foothold. Currently geothermal power qualifies for two Renewable Obligation Certificates (ROCs) per MWh of electricity generated, but the investment community believe this support should be closer to four ROCs, so that investment doesn’t go to other parts of Europe like Germany.
Geothermal power electricity is currently produced in 24 countries across the planet with the total combined installed capacity being approximately 10,715MW. The largest capacity is in the USA (3.1GW installed in 2010), however by 2015 this is expected to increase by 75%, taking installed capacity to 18.5GW. Geothermal power as a heating solution is much more widespread, and currently used in over 70 countries worldwide.
The largest geothermal power company in the world at present is the Calpine Corporation which taps geothermal electricity primarily in the geysers in California. The 19 geothermal power plants it has in this location provide 25% of the green energy to California. In the UK, the Eden Project in Cornwall was granted permission to build a hot dry rock geothermal power station in December 2010, which will power Eden and supply enough energy for 5000 additional houses in the surrounding area.
When air hits the wind turbine, the blades spin, converting the wind’s kinetic energy into mechanical energy. This rotary motion then travels down the shaft and drives a generator where the electricity is produced. Typically most wind turbines are mounted in the horizontal plane (like the propeller of a plane), and therefore it is key the blades are facing directly into the wind.
The yaw angle is the difference in angle between the wind direction and the direction in which the rotors are facing. The aim is to minimise the yaw angle as much as possible, so most residential wind turbines tend to have tails which orientate the turbine to best capture the wind. Wind turbines should therefore be able to rotate 3600 on yaw bearings.
There are 2 main styles of urban wind turbines:
Horizontal Axis Wind Turbines (HAWT)
This is a propeller type rotor mounted on the horizontal axis. As mentioned previously, the blades need to be aligned with the wind and this is done by either a simple tail, or an active yaw. These are more efficient at producing electricity than VAWTs however they are impacted more by changes in wind direction.
Vertical Axis Wind Turbines (VAWT)
These are aligned in the vertical axis (like the rotor blades on a helicopter). These are only really deployed within urban areas, where the flow of air is more uneven. Due to their alignment, wind direction has little impact on this type of turbine; however it is apparent that these are less efficient than their HAWT cousins.
In addition to HAWTs and VAWTs there are hybrid turbines that are cylindrical (imagine a gyroscope) – such as the energy ball.
At TheGreenAge, we suggest sticking with the HAWTs as they are the more proven technology, and are offered by more suppliers, so you will be able to get better value for money.
Most turbines tends to have two or three blades, two bladed turbines are cheaper but suffer from blade chatter which puts stress on the system, which can lead to increased maintenance further down the line. If you can afford to get a three bladed turbine, we suggest doing so, as these don’t suffer from this problem at all.
Three types of tower exist: tilt-up, fixed guyed and free standing. The purpose of these towers is to position the turbines in the best possible position to take advantage of the wind.
Tilt-up towers are held in position by four guy ropes one of which can be released, allowing you to lower the tower, so you can work on the turbine.
Fixed guyed towers are similar to tilt-up towers, except they are permanently fixed in place so you need to climb the tower to do any maintenance.
Free standing towers have no guy ropes. As such they require a very solid foundation. Therefore these are certainly the most expensive, but may well be the most aesthetically pleasing.
Most wind turbines produce AC current, so this should be able to be directly fed into your home and the grid, however the voltage and frequency of the power produced is very erratic, so an inverter is used to convert the erratic AC to DC, then back to a smoother AC which can be synchronised with the grid, or for use directly into your home. Battery-based wind turbines normally operate at 12 or 48 Volts, and therefore the inverter must also act to convert this relatively low voltage to high voltage (UK mains is 240 volts). Battery-less systems may produce electricity with a voltage significantly higher (100 volts or more). Therefore in this situation, the inverter needs to be able to handle this higher voltage.
In most wind turbine systems, the electricity does not power any appliances directly. Instead the electricity produced is stored in deep-cycle lead acid batteries which look very similar to the ones found in most cars today (although structurally different). The two most popular types of battery are GEL and Absorbed Glass Mat (AGM), which store the charge very well and do not degrade nearly as fast as the common lead acid (wet cell) battery. Both types of batteries are designed to gradually discharge slowly and recharge 80% of their capacity hundreds of times.
An automotive battery is a shallow-cycle battery, and this is designed to discharge only about 20% of its electricity so is unsuitable for solar photovoltaic cell set-up. The reason is that if any more than 20% is drawn more than a few dozen times, it will get damaged and no longer take charge.
Wind turbine batteries tend to operate at 12v, and can be arranged in banks (multiple batteries), increasing the storage potential of your wind system set up. A bank of batteries organised in a series increases the capacity of your storage but also increases the voltage delivered from your bank; while multiple batteries organised in a parallel circuit increase the capacity, but the voltage stays the same.
Charge controllers are used in wind turbine systems to prevent the batteries from being overcharged. If you decide to implement a grid tie system, a charge controller is not necessary, as any excess electricity that you don’t use at any particular moment is sold directly back to the grid. However, for any battery setup, a charge controller is necessary as it prevents damage to the battery by monitoring the flow of electricity in and out. If your system overcharges the battery it will damage it. The same is also true if you completely discharge all the charge held within the battery.
Most charge controllers associated with wind turbines have dump load capability associated with them. This allows any additional charge to be diverted from the batteries when they are full, potentially to a hot water heating system (so the electricity is not completely wasted). Obviously if you are connected to the grid, this electricity would instead be sold there, providing you with an additional income stream.
Most charge controllers are also equipped with maximum power point (MPPT) charging. The principle of MPPT is to extract the maximum available power from the wind turbine by making them operate at the most efficient voltage (known as the maximum power point voltage). The algorithm included in the MPPT charge controller compares the output from the wind turbine with the battery voltage and then fixes it at the best charging voltage, to get the maximum charge into the battery.
Disconnects are simply switches that allow you to isolate parts of the system so you can troubleshoot or repair faulty parts without the risk of being electrocuted. In addition many wind turbine systems are grounded, so that if there is surge in current anywhere in the system it is safely dissipated rather than damaging the system or more importantly you!
Installing a wind turbine
Are you thinking about installing a wind turbine at home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer to help install a wind turbine at home, just fill in the form below and we will be in touch shortly!
CHP cogeneration (combined heat and power for industry) follows the same processes and principles as micro CHP boilers, but on a grander scale. When a fossil fuel power station produces electricity, it also produces a lot of waste heat. In fact, 65% of the energy potential contained in the fuel turns to heat and only 35% is actually converted to electricity, which shows that there is a large efficiency gap. The heat produced is in the form of steam, which is used to drive the electricity-producing turbines. When you drive past a power station you will have probably have noticed the large cooling towers releasing this steam into the atmosphere, which highlights the wasted heat.
The unique point about CHP Cogeneration is that it captures this steam and reuses it for other purposes, such as providing heating for local districts or towns that are close to the plant. In other cases CHP cogeneration plants can fit in tandem with existing industrial processes; for example the production of sugar beet or providing steam to refineries.
Types of CHP cogeneration
As mentioned in the CHP boilers section, CHP cogeneration is underpinned by a number of different technological processes. The process that creates the energy required can either be a combustion process or a fuel cell chemical reaction. Both of these processes produce the heat and power to ensure they can be used for the purposes of CHP Cogeneration. A summary of the technological processes is in the sub-section below:
Combustion CHP Cogeneration
The structure of CHP cogeneration plants usually takes the form of an external combustion engine, which has been a technology widely used in steam engines. Many fuels can be utilised to produce the heat required including gas, coal, biomass, nuclear and geothermal. The fuel is combusted and this heats water, which is then forced into a pressurised boiler. This heat and pressure feeds the main engine or a turbine, which then rotates. The rotating motion then simply spins a large magnet (main engine) inside a coil of copper wire, known as the generator. This then completes the process of converting mechanical energy into electrical energy.
The difference with CHP cogeneration and other plants is what happens with the steam and heat generated from the boiler that then leaves the system. If the infrastructure is in place, this heat can be released out of this process and potentially pumped to a nearby facility for a different purpose altogether. Some of the secondary activities that heat can be utilised for are, district heating (as discussed above) and to drive newly built water desalination plants.
You can also have CHP cogeneration with power plants that are not primarily there to generate electricity but that are there to support additional industrial processes. For example, a bottoming cycle industrial plant produces high temperature heat for an industrial process such as glass furnacing or metal manufacturing. In addition, a waste heat recovery boiler recaptures waste heat from the manufacturing heating process. This waste heat is then used to produce steam that drives a steam turbine to produce electricity. Since fuel is burned first in the production process, no extra fuel is required to produce electricity. In the 1990s British Sugar built a state-of-the-art CHP plant, using excess heat and electricity to support some of its secondary processes – as well as providing district heating.
Fuel Cell CHP Cogeneration
An emerging CHP cogeneration technology is the fuel cell, where fuel, such as natural gas, is converted to electricity in a chemical reaction rather than a combustion process. Again, let’s talk a little bit first about this fascinating science. First requirement is to have solid oxide fuel cells (SOFC), which are allowed to operate at high temperatures. The fuel cells then on one side chemically interact with a fuel input (LPG, natural gas, hydrogen for example) and on the other side with air. This combined reaction – using an anode and a cathode – and is then able to produce electricity and heat (up to 1000 degrees centigrade).
The development of this technology for CHP cogeneration is ongoing, so that one day it can be used as a standard solution for both businesses and homes. Companies such as Mitsubishi Heavy Industries in Japan are looking at ways of introducing this process alongside conventional combustion processes. An example of how this is utilised could be when a company is enhancing existing gas plants with fuel cell technology, to make sure the levels of efficiency increase. As we have already mentioned, the electrochemical process from fuel cells produces heat, and this is then separately captured and used in a secondary process. For example the heat can be used to create steam, which can then feed a combustion system to create secondary electricity. Any excess heat can be recycled further and used to supply district heating or to enable further industrial processes to take place. These processes and recycling heat for multiple uses, increases plant efficiency, which ensures that as little heat as possible is wasted.
CHP cogeneration industry development
The principles of CHP cogeneration have been around since the 1960s in the UK. For example the Combined Heat and Power Association (CHPA) was set up in 1966 as the District Heating Authority to highlight benefits of district heating, but now it is there to highlight the benefits of taking an integrated approach to heat and power. Industrial and domestic CHP cogeneration generators of electricity can currently make use of the Renewable Obligation Certificates (ROCs) and Feed-in-Tariffs (FiTs) respectively. More on this in the section below, as well as an explanation of the Renewable Heat Incentive (RHI) in more detail.
In the UK, the Immingham CHP cogeneration plant (one of our featured case studies), has been in operation since 2004, producing 1.2GW of electricity, making it one of Europe’s largest CHP cogeneration plants. Some of its uses are as follows: providing steam and electricity to the Humber Refinery, steam to a neighbouring refinery, and power back into the grid.
Now a bit about our neighbours in Europe: CHP cogeneration is already used on a commercial scale in many Scandinavian countries, with 40% of Denmark’s total electricity capacity derived from this source, as is 30% of Finland’s. Germany on the other hand has also made its intentions clear in support of the technology. This signal was made clear since it decided to scale down and decommission the existing civil nuclear power plant project. However other parts of Europe like the UK have a lot of catching up to do to these countries.
Cogeneration CHP UK public policy
The DECC policy is to support measures such CHP cogeneration as well as solar commercial power plants, wind farms and nuclear power to ensure that by 2020 the UK is in a good position to meet its emission reduction targets. The main policy areas that cover CHP cogeneration are summarised below:
Renewable Obligation and Feed-in-Tariffs
ROCs are available to commercial electricity generators of CHP cogeneration, which are usually ones that are able to demonstrate the production of multiple MWh of electricity production (also considered a metric that symbolises the starting point for mass scale consumption). The level of support varies depending on the CHP cogeneration type. For example, if combusting waste CHP cogeneration, then level of support is 1 ROC per MWh. On the other hand, if you are using dedicated biomass fuel with CHP cogeneration, and can demonstrate sustainable fuel supply, then the entitlement increases to 2 ROCs per MWh.
FiTs on the other hand are an initiative to support micro generators of renewable electricity. If you are a small business or a community project (and this is your first time involvement in electricity generation), please note to satisfy the FiT criteria, you need to have a declared net capacity greater than 50kW and up to and including 5MW (2MW for micro cogeneration CHP). Income can be earned both from the generation tariff and the export tariff.
These two policy areas are great incentives if you are looking to invest in renewable CHP cogeneration projects or if you are looking to start up your own renewable CHP cogeneration plant.
Renewable Heat Incentive
The RHI is a payment subsidy (pence/kWh), for heat and hot water generated by households or businesses, using an eligible renewable technology, which includes CHP cogeneration.
In March 2012, the DECC set out a roadmap for district heating incentives. This has called on improvements to infrastructure around existing power plants and newly built ones to extract some of the excess heat and provide it for local homes and businesses. An apparent lack of investment in infrastructure is to blame for a lack of district heating incentives in this country. Everything in the UK is dug underground from electricity cables, telephony and natural gas distribution. District heating incentives for example would struggle to compete with existing infrastructure in large conurbations, but there appears to be an opportunity for connecting new out of town developments and/ or areas of the country which are currently off-grid.
Examples of some of the CHP cogeneration initiatives that could be implemented in the UK are as follows: heat from gas-fired CHP plants, biomass and biogas, heat pumps, energy-from-waste, solar thermal, excess heat from industrial processes and power stations. These processes are very common in Denmark, and as previously mentioned, are enablers used for helping the process of decarbonisation of the economy.
Installing Micro CHP
Interested in installing a micro CHP boiler? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local installer to help install micro CHP in your home, just fill in the form below and we will be in touch shortly!
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