Crescent Dunes Solar (CSP) Energy Plant Background

In September 2011, construction began at the Crescent Dunes Solar Energy Plant, a 110MW concentrated solar power (CSP) plant located near Tonopah, Nevada.  SolarReserve, a US-based developer of large-scale solar power plants, is developing the Crescent Dunes Solar Plant utilizing its market-leading solar power technology with integrated energy storage to deliver clean, reliable electricity on-demand, 24-hours a day. The 540 foot solar power tower, which is located in the centre of the overall plant layout, was completed in February 2012.

Crescent Dunes Solar Energy Plant Key Operating Facts

Unlike most solar plants, which are made up of rows of interconnected solar photovoltaic (PV) unit, the CSP technology at the Crescent Dunes Solar Energy Plant uses thousands of mirrors to concentrate the sun’s energy to the 100-foot tall heat exchanger that sits at the top of the central tower and captures the sun’s energy using liquid molten salt, which is heated from 500 to 1050 degrees Fahrenheit.

The Crescent Dunes Solar Energy Plant will use approximately 10,000 mirrors, called “heliostats”, to direct sunlight towards the receiver at the top of the solar tower, each heliostat continually moving to track the sun and maximise the amount of thermal energy that the tower receives. In technology similar to SolarReserve’s, the heat is used to superheat water to generate steam to drive a steam turbine, but this is not the case in SolarReserve’s technology. SolarReserve’s technology uses molten salt to both capture the sun’s energy and then store the energy, which allows the plant to generate steam for a traditional steam turbine whenever electricity is needed, even after dark.

Comparing Traditional Solar PV to SolarReserve Technology

Previously solar energy, such as Solar PV, has largely been considered an intermittent energy source (like wind farms), meaning that the plant can only generate electricity when the sun is shining. Traditional solar plants can’t produce electricity at night, and even cloudy days or other forms of shading impact the total output of the solar plant. However, SolarReserve’s technology has found the solution to intermittency through the use of integrated energy storage. The molten salt solar thermal power technology that will be used at the Crescent Dunes Solar Energy Plant allows the plant to produce electricity 24×7.

At the beginning of the day, the “cold” molten salt, which is held at a temperature of about 500 degrees Fahrenheit, is pumped up from the “cold” storage tank, up the tower, and into miles of piping that run through the walls of the receiver that sits at the top of the solar tower. Here, the molten salt is heated from 500 degrees to 1050 degrees Fahrenheit by the sun’s energy and then pumped back down the tower to the “hot” salt storage tank where the thermal energy is stored.  When electricity is needed, the hot molten salt is used to generate superheated steam to drive a standard steam turbine. After the hot salt is used, the cooler molten salt is then pumped back into the cold salt storage tank for the process to be restarted once again.

Crescent Dunes Solar Electricity Potential

As the electricity generated by the Crescent Dunes Solar Energy Plant will provide electricity to Las Vegas, this 24/7 electricity generation potential is perhaps a prudent measure! SolarReserve will sell 100% of the electricity generated to NV Energy, Nevada’s largest utility, under a 25-year Power Purchase Agreement.

It is estimated that Crescent Dunes Solar Energy Plant will generate approximately 500,000MWh of electricity per year, which is double the amount of electricity that would be generated by a similarly-sized PV plant, and is enough electricity to power over 75,000 houses during peak electricity periods.

Crescent Dunes Solar Power Plant Environmental Impact

Despite producing an abundant, clean source of electricity, the CSP plant may impact the environment. Obviously the mirrors are concentrating an incredible amount of heat at a very small area, posing a danger to anything that gets in its way. Any wildlife, such as birds, that come into contact with this sort of heat will be in serious trouble. In addition, the diameter of crescent Dune mirrors is 2 miles, so it is taking up serious acreage to fulfil its role.

On the whole though, the Crescent Dune Solar Energy Plant seems like a great engineering feat, providing clean electricity 24/7, in a much more efficient way than existing solar PV technology.

As part of the Green Deal, I am going to a lot homes at the moment and solar PV tends to come up a lot. People are unsure about how the numbers stack-up, they have heard in the news about the recent drop in the Feed-in-Tariff payments, but they are also aware that energy prices are going up substantially every year. So is getting solar PV installed on your home still worth it?!

In a word – Yes!

But the speed of payback is actually fairly dependant on when you use the energy, as you will see in a minute. So here goes and if you want to query any of the numbers, please drop a comment at the bottom of this post. A typical system is about 3.6kW (3,600 watts) in size, which will cost you approximately £6,000.

How much electricity will your Solar PV system Generate?

If you take this figure (or the size of the system you are interested in getting – obviously the bigger it is the more electricity it can produce) and multiply it by 0.8 it will give you the approximate number of kWh the system produces in a year, so in this case a 3.6kW system would work out as follows.

So 3600 x 0.8 = 2880kWh

To give you a rough guide, the average home uses about 4,800kWh each year, although your energy bills will reveal what you actually use.

The Generation Tariff – payment for every kWh of electricity produced

As part of the Feed-in Tariff, the Energy Suppliers are obliged to pay you 15.44 pence for every unit of energy you produce, regardless of what you do with it – this is known as the Generation Tariff and is guaranteed for 20 years, i.e. regardless of whether the FiT drops over the coming years, you will get this payment of 14.90 pence for every kWh you produce.

2880kWh x 14.38 pence = £414.14

But there is more!!

The Generation Tariff is only half the story!

Now unfortunately, as anyone who has done GCSE science will be able to tell you, it is not possible to store electricity so you can either use the electricity as it gets produced by the solar PV system or you can export it back to the electrical grid (you have have battery back-up, however in the UK 99% of homes with Solar PV have grid-tied systems).

The final payback of the system is dependant on the ratio of using the electricity in the home compared to the amount exported.

The Export Tariff – payment for every kWh of electricity exported

For every kWh produced and sold back to the grid you get 4.77 pence (this is known simply as the Export tariff), but for every kWh you can use in the home, it means you don’t need to buy it from the grid at approximately 15.32 pence / kWH.

I hope you can see therefore that it is about 3 times better (financially) to use the electricity you produce rather than export it back to the grid.

Having said all that – it is worth bearing in mind that most residential solar PV systems installed in the UK don’t come with a export meter, so they will simply half the generation meter reading and assume you export that this – this means you will be paid as if you exporting 50% regardless of whether you use all the electricity in the home or none of it.

As a result of this – in an ideal situation you would use 100% of the electricity in the home and you would still be paid as if you were exporting 50% of it to the grid – so a nice little bonus!

In the scenarios below however, I am going to include the export calculations as if you have an export meter, since the move to smart meters will unfortunately remove this nice little bonus!

Maximising the return from your Solar PV investment

So the key here is obviously to have lots of panels, all facing south, and use every kWh of electricity that they produce, however in most cases this simply isn’t feasible.

Imagine being at work all day, your solar system is producing lots of electricity, but you aren’t there to use it. Conversely, a stay at home mum would be much better placed to use all the electricity.

So in the next section I am going to look at 3 scenarios which will determine the amount of electricity a household can use in the home and how much they need to sell (remembering you can’t store the electricity), and therefore their total yearly return from installing a 3.5kW solar system within their home.

Scenario 1 (Parents both working, children at school)

In this scenario, it makes sense that the family will only be able to use their energy early in the morning and when they get home in the evening (obviously they can set washing machines / dishwashers to run as they leave the house), but lets say they use 25% and sell 75%.

Export tariff – 75% x 2880kWh x 4.77 pence = £103.03

Saving on Energy Bill – 25% x 2880kWh x 15.32 pence = £110.30

Total Yearly Return = £414.14 + £103.03 + £110.30 = £627.47

Scenario 2 (1 Stay at home parent, other at work and children at school)

In this scenario, while parent at home will use a decent proportion of the electricity produced, it will be nowhere near the usage if all the family where at home at the weekend for example. In this example lets say usage is about 50% and therefore 50% needs to be sold back to the grid.

Export tariff – 50% x 2880kWh x 4.77 pence = £68.69

Saving on Energy Bill – 50% x 2880kWh x 15.32 pence = £220.60

Total Yearly Return = £414.14 + £68.69 + £220.60 = £703.63

Scenario 3 (retired grandparents at home for the majority of the day)

In this scenario, the vast majority of the electricity that is produced will be used in the home, so I am going to use the ration 80:20.

Export tariff – 20% x 2880kWh x 4.77 pence = £27.47

Saving on Energy Bill – 80% x 2880kWh x 15.32 pence = £352.97

Total Yearly Return = £414.14 + £27.47 + £352.97 = £794.58

Maximising your solar PV return

It goes without saying that the bigger your solar array, the more electricity it will produce, but how else can you be sure you are maximising your return?

Orientation of the panels

Solar panels in the northern hemisphere perform best when facing due south. This ensures that they receive the maximum exposure from the sun as it travels east to west. There is little point putting solar panels on a north-facing roof, so you may need to install them on a solar array mounting on the ground to ensure you can get the panels angled in a southerly direction.

There are different types of solar array mounting, but you can get fully automated tracking solar mounts. These mountings track the movement of the sun to ensure that the angle of the solar array is maximising exposure to sunlight at all times. These are expensive, but they also make sure you are getting the best yield.

Casting shadows on your solar PV array

It is important to ensure that shadows won’t fall on the solar panels during the peak sunlight hours, as this will obviously adversely affect the output of your solar system.

The effect of shadowing is amplified if your solar PV array has been set up with string inverters. In this setup, each panel is connected to the next panel in a series of strings, with each panel feeding a DC current to the inverter. When a cell underperforms, bypass diodes reroute the current around the underperforming cells. The problem is that rerouting the current loses not only the potential energy from these cells, but also lowers the entire string’s voltage.

The inverter then has to decide whether to optimise the voltage of the underperforming string or maximise the energy harvest from the unaffected strings. Normally the inverter chooses to optimise the voltage of the underperforming string, causing the performance of the whole string of panels affected to drop significantly. Just 10% shading of a solar PV panel can result in a 50% decline in output in this type of setup.

Solar arrays with micro inverters do not suffer anywhere near as badly from shading compared to the arrays with string inverters.

As a result of the shading issue, it is important to ensure that shadows won’t fall on the solar cells during peak sunlight hours as this will obviously adversely affect the output of your solar system. It is also important to have the foresight to predict tree growth in the coming years, as solar panels should go on producing electricity for 25 years; therefore trees that are currently of no concern could very easily grow to sufficient size in 15 years to cast shadows, diminishing the power producing capability of the solar photovoltaic system.

Keeping your solar panels clean

The operating efficiency of a solar PV panel is dependent on the amount of sunlight that hits it, so if you panels are covered in dirt they are going to produce less electricity. It is suggested to wash your solar panels 2-3 times per year for maximum efficiency. We cover the various techniques for cleaning your solar array here.

You should also coat your solar panels with protectant to reduce reflection and increase transmissivity.

Ambient temperatures of the panels

One of the key factors impacting the amount of electricity your solar panels produce is the temperature at which they operate. It is easy to presume more sun and therefore heat results in more electricity but this is wrong. Different solar panels react slightly differently to the operating ambient temperature, but in all cases the efficiency of a panel will decrease as the temperature increases.

The negative impact of temperature on solar panel efficiency is known as the temperature coefficient.

Solar panels are power tested at 25⁰C, so the temperature coefficient percentage illustrates the change in efficiency as it goes up or down by a degree. For example if the temperature coefficient of a particular type of panel is -0.5%, then for every 10C rise, the panels maximum power will reduce by 0.5%.

So on a hot day, when panel temperatures may reach 45⁰C, a panel with a temperature coefficient of -0.5% would result in a maximum power output reduction of 10%. Conversely, if it was a sunny winter’s morning, the panels will actually be more efficient.

It is therefore really important to maximise airflow around the panels to try to keep them cool so their efficiency isn’t negatively impacted. Rather than installing panels flat against your roof, you could try lifting them slightly to allow air to circulate underneath.

Use more of the electricity in your home

As mentioned in the solar PV costs section, it is best to use the electricity you produce from your solar PV array in your home, since that means you don’t need to buy it at 15p from the electricity company. Selling the electricity back to the grid means you are eligible for the export tariff which is only 4.5p/kWh.

One way to do this is with a solar diverter. These send excess energy that isn’t being used by your appliances to your immersion heater instead, helping to heat your water.

You can also make behavioural changes to ensure that you are using as much of your self-generated energy as possible. It is worth changing some of your energy usage behaviour. For example, it is better to run washing machines and dishwashers during the day – so set them to start as you leave for work.

The other way to use all the electricity you produce is by incorporating batteries into your solar PV array. Batteries will increase the upfront cost of your array and will require maintenance, but can be really worthwhile in the long run. Any electricity you produce during the day can be stored in the batteries and then used as and when you require it.

Final thoughts on investing in a solar PV system

Having received quotes for solar PV installation, you need to run the numbers to see if it makes financial sense for you to invest. It is important to bear in mind though, that solar photovoltaic arrays are modular, therefore new panels can be introduced at later dates as finances allow, further increasing the electrical output potential of your system.

Installing a solar photovoltaic array on your property should not be solely a financial decision though; you should also take into account energy security.

As demand for electricity in the UK continues to increase, the supply side is not keeping up. Over the next 3 years, 8 of the UK’s coal power plants are going to close, due to EU legislation on emissions, and by the end of the decade some of our nuclear capacity is also due to be decommissioned. Experts have predicted that the UK could face blackouts in the next few years.

A solar photovoltaic system can therefore reduce your reliance on energy companies, helping to minimise the impact of energy scarcity on you and your family in the future.

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!

2013 started pretty well for the renewables industry with news that Warren Buffett is investing a further £1.5bn in what will become the largest solar PV development in the world.

Mr Buffett is widely regarded as the most successful investor of modern times. Although coming from a fairly privileged background, his shrewd investments resulted in him amassing billions of dollars. In 2012 he was voted the fourth richest man in the world with a net worth of around $46.4bn, according to Bloomberg.

Time and time again Mr Buffett has made the right investment decisions, despite an uncertain market, therefore if he feels that now is the time to expand his investment in renewables, one can take it as a very positive sign that they are going to play a major role in the future, not just because the ‘greenies’ are banging the drum, but because they are going to offer excellent returns.

 The latest investment sees Mr Buffett’s MidAmerican Energy Holdings investment company striking a deal with SunPower to acquire and build 2 solar PV projects in California. The two projects acquired by Mr Buffet have a combined capacity of 579MW, and will be completed in 2015. In December 2011, his investment company acquired another 550 MW solar PV plant from First Solar. Already MidAmerican Energy Holdings has invested more than $10bn in wind and solar energy, and we hope there is more to come!

According to a report completed by the Federal Energy Regulatory Commission’s Office of Energy Projects, for the first nine months of 2012, 43.8% of the new capacity added in the US was from renewable sources (e.g. wind, solar, biomass, geothermal and water power). Renewables accounted for 13% of total electrical generation during the first six months of 2012 in America.

In the UK, renewables supplied 11.7% of our energy requirement in Q3 2012, but this figure may have been significantly higher if there had been more rainfall during the year (hard to believe, but there were actually hosepipe bans in place in March 2012!). The installed capacity for 2012 was also up 46% on the previous year, due to large wind projects being completed and the conversion of the Tilbury Power Plant to run on biomass.

So despite all the doom and gloom around the economy, it appears investment in renewable energy is looking very healthy!

What is the Solar Power Tipping Point?

The solar power tipping-point is coming. In fact, in some countries with particularly high energy costs and lots of sun (like Hawaii), it has already been reached. The tipping point, also known as grid parity or the golden goal, is the moment when solar produces power at the same price as electricity from the grid. At this point, energy produced from solar sources will match other more traditional sources such as coal, or even gas.

At the moment, the reason for putting solar PV (photovoltaic) panels on your roof in the UK is an economic one. It is the direct result of the feed-in tariff (and to a lesser extent the export tariff), which is the government policy which pays you per kWh of electricity you produce. This helps to create an artificial economy for solar PV, by increasing demand and driving uptake.

How is Solar Power going to reach the tipping point?

To hit true parity though, solar PV needs to become competitive without this helping hand. So how is this happening?

The major reason is the massive price drop in the silicon PV modules. In 2011 the price of these modules halved, as the result of two things. Firstly, huge new solar production facilities opened across the world, particularly in China, increasing competition and actually driving smaller facilities in Europe out of business. Germany once had a world beating solar energy industry, accounting for a 20% market share in the global solar market. It now accounts for just six per cent. Secondly, technology is improving and there are increased economies of scale, which has resulted in modules coming down in price by 18% for every doubling of capacity.

Existing energy prices can also only go one way – up. With ageing infrastructure and a lack of capacity in the UK, investment and modernisation will have to be made. This will be subsidised through higher energy bills. As the supply of fossil fuels decreases or fuels become harder to source, producers will have to drill deeper or use more expensive methods.

So these mechanisms are driving us towards the tipping point, but there are also barriers to us getting there. Firstly, solar PV is still costly in the short term – £7,000 or more for a system with a decent payback. Compare this to electricity from the socket at 12p/kwh.  In the current economic climate people are unable or unwilling to pay for the installation. Obviously the higher the uptake, the higher the supply and the quicker economies of scale are introduced into the production process.

Solar PV is also intermittent: electricity is only produced when the sun is shining. There are solar PV plants in the USA that are planned to have integrated molten salt technology, which essentially will allow power stations to produce electricity 24/7, but this just isn’t viable for the domestic user. Therefore solar can’t be the only solution. It is not suitable to provide the base load in the energy mix. I think nuclear energy (either existing fission plants, or Thorium molten salt) would be best to provide the base load, which would subsequently be topped up by solar PV technologies.

Also if solar PV installations are to become commonplace in the UK, we need to make changes to the grid. In comparison to traditional power plants, solar PV installations take up much more space (per square metre). Therefore what is needed is a shift from a centralised utility grid to a decentralised grid, which will again require more investment.

Finally it is worth briefly examining the feed-in tariffs (FiT) and other subsidies; late last year the FiT for UK solar was £0.433 for every kWh of energy produced. This was cut to £0.21 in May 2012, and is due to be cut to £0.16 at the beginning of August. The FiT is supposed to support the uptake of solar energy in the UK, but the government’s decision to make such a large cut in the FiT in May had a very negative impact on the UK solar industry. Obviously the FiT should be decreased in line with falling solar module prices, but this decrease and the cuts should have been far more gradual.

In conclusion, solar will hit the tipping point and reach grid parity. It may not happen in the UK over the next couple of years, but the signs are there that it will happen by 2020. At this point, the decision to invest in either traditional fossil fuel or solar PV will hopefully become more obvious for the government.

What is the Smart Export Guarantee?

After the closure of the Feed in Tariff (FiT), the government introduced The Smart Export Guarantee (SEG) which launched in 2020. The scheme allows growth in electricity generation from green microgeneration technologies.

How does the Smart Export Guarantee work?

Licensed electricity suppliers can offer a tariff and make payment to small-scale low-carbon generators for electricity exported to the National Grid (considering certain criteria are met).

The following low-carbon, renewable technologies are eligible for the SEG:

• solar panels (solar pv)
• wind turbines
• hydro electricity
• micro combined heat and power
• anaerobic digestion

If you decide install any of the above renewable generation for the home, you should be eligible for the SEG tariff, providing you meet certain criteria.

• Your installation must be 5MW capacity or less (50kW for micro-CHP).
• You need to take electricity readings from your meter – this is going to be easier if you have a smart meter installed, which will automatically take the readings for you.
• Your installation must be MCS-certified.

Savings on electricity bills

Every kWh of electricity that you create yourself and then use in your home means that you don’t need to buy that unit from the electricity company. Electricity is currently priced at about 15 pence/kWh when you buy it from any of the big six energy companies, so the more electricity you produce and use in your home, the more you save.

Smart Export Guarantee registration

In practice in the UK, the energy companies with over 150,000 customers (British Gas, EoN, SSE, Scottish Power, EDF and NPower, etc) are required by law to provide the SEG to homes and businesses. Other smaller electricity suppliers may not offer the SEG as it is not compulsory for them to do so. The full list of registered SEG licensed suppliers is available on the OFGEM website here.

Once you have the product installed through the MCS, you should receive a certificate confirming MCS compliance. Speak to your energy company  that is approved for the SEG – express your interest in receiving the SEG. Your supplier will confirm your eligibility, cross checking your details to the MCS database. On confirmation of the SEG your details will also be added to the OFGEM Central SEG Register.

You may also need to agree a process for meter reading and whether you want to opt out from export tariffs. An important point to note is that it is far more economical to use as much of the electricity you produce in the home as you can, rather than selling it back to the grid. Using a kWh of the electricity you produce in your home saves you buying it from the energy suppliers at 15p, while you can only sell it back to the grid for 4.77p.