What is hydrogen?

Hydrogen is the most abundant element in the universe but naturally occurring hydrogen on earth is rare. This is because it is highly reactive, and so it reacts with most elements to form compounds that we see around us today. Hydrogen is found in pretty much all the food we eat, in fossil fuels to power our cars and also in water, which is made up of two hydrogen atoms combined with one oxygen atom.

If hydrogen is isolated and ignited with a flame in air, it will combust fiercely and produce heat and water as a by-product. There are already cars that run solely on hydrogen, which means that these cars are 100% emission free. So hydrogen is abundant and combusts with zero dangerous emissions, which makes it a perfect candidate for energy storage.

How can hydrogen combat volatilities in electricity demand?

Many countries have electricity demand volatilities, where a large amount of electricity is needed at rush hour, and again when people come home and use appliances during the evening. Conversely, while people are asleep at night, demand is much lower. This is a rather simplistic model, but it demonstrates the electricity demands of the modern world.

Unfortunately electricity cannot be stored, and at the moment most is either used or wasted as it is produced. However, if we intervene correctly we can transfer the excess electricity into another form of potential energy such as hydrogen. It can then be used to create electricity when required, thereby reducing the volatility of demand on the grid.

Producing hydrogen for grid storage

The main commercial process used for creating pure hydrogen is steam reforming, which involves breaking down a hydrocarbon into hydrogen and carbon monoxide.

However, as an energy storage measure for the grid, the most suitable method of creating hydrogen is through a process called electrolysis, which is simply using electricity and water. Importantly, hydrogen can be produced using electricity sourced from renewable sources such as wind and solar. Therefore when there is excess supply capacity, such as during the night when demand is also low, this excess electricity can be used to produce the hydrogen.

The process of the electrolysis of water involves passing an electrical current through water, which then produces pure hydrogen gas and oxygen. Two electrodes are positioned in the water, and when an electrical current is passed down the cathode (the negatively charged electrode) hydrogen bubbles out, while at the anode (the positively charged electrode) oxygen is released.

Another potential mechanism for making hydrogen is using algae or cyanobacteria, which use the sun to split water into hydrogen and oxygen. Under normal conditions, however, hydrogen production is secondary to the production of compounds that the organisms use to support their growth. However specialised enzymes can be introduced to suppress sugar production in the organism so it produces much more hydrogen gas. This research is still at an early stage, but the paper that describes the process can be found here.

What do we do with the hydrogen sas produced?

This hydrogen gas can then be stored and used in a fuel cell to create electricity (or it can be burnt to power a traditional turbine/ generator system). In a fuel cell, the hydrogen is combined with oxygen to create electricity without producing any heat. There are several advantages of producing electricity with a fuel cell rather than combusting the hydrogen. The fuel cell operates very efficiently, is very reliable and the only by-product is water – an obvious environmental bonus.

The future for hydrogen mass storage

The future seems bright for hydrogen as a mass storage technique. The ability to create hydrogen by applying an electric current to water when there is excess supply in the grid is a very simple process. ITM Power, based in the UK, are currently building an infrastructure to create hydrogen on a large scale by using electrolysis to power industry and road vehicles.

The electrolysis units are then positioned where the gas is required. This removes the cost of implementing the infrastructure required to pump the hydrogen between locations, or to carry the hydrogen gas in lorries.

The test units they currently have in operation create 5kg of hydrogen gas over a 24-hour timeframe. It takes roughly 60kWh of electricity to produce 1kg of hydrogen and that would cost about £7.20 at today’s electricity prices. If this was used in car it would work out at about £0.12 / mile, where as a traditional petrochemical engine would work out at about £0.18 / mile.

However if the electricity required to make the hydrogen was sourced 100% from renewable technologies, then the whole process would be 100% emission free.

The major issue with hydrogen gas

Whilst hydrogen does sound like a genuine mass storage contender, there is one main issue with it, which is storage. It is difficult to store because it has very low volumetric energy density. It is 3.2 times less dense than natural gas and 2,700 times less dense than gasoline. Therefore to store it, it needs to be compressed, liquefied or chemically combined prior to storing. A standard method to do this on a large scale needs to be formalised to ensure that it becomes economical to store the hydrogen.

Could hydrogen be the answer to grid energy storage

In a word, yes! Producing hydrogen can be done now and hydrogen has a very high specific energy (energy per unit mass). However the mechanism for producing the gas has to be standardised so economies of scale are introduced into its production, helping to bring the cost of production down.

The major drawback with hydrogen is that it takes up such a large space when it is stored. Therefore new, more effective storage processes will need to be introduced, to make its storage economically viable. Rather than turning off wind turbines to prevent excess electricity going into the grid, hydrogen storage in fuel cells is an excellent way to conserve energy.

What is a capacitor?

A capacitor is much like a battery, but instead of using a chemical reaction to create a flow of electrons and therefore provide power for an appliance, the capacitor stores electrons.

As such a capacitor is far simpler than a battery, and is used in all sorts of electronics today, to provide a small amount of electricity storage.

What is inside a capacitor?

A basic capacitor consists of two metal plates separated by a non-conducting substance known as a ‘dielectric’. In theory the dielectric substance used can be any non-conducting substance, but in practise specific materials are used such as porcelain or mica to give the capacitor particular features to fulfil its role.

How does a capacitor work?

When a capacitor is in an electric circuit, the electrical source pushes negatively charged electrons on to one of the metal plates. The dielectric substance in the middle prevents the movement of these electrons across the circuit, so this plate becomes highly negatively charged and a positive charge builds on the other plate.

When the repulsive force of the negatively charged plate becomes large enough, it repels further electrons from approaching the plate, and at this point the capacitor is charged. The capacitor can then discharged, which involves allowing the electrons to complete the circuit, providing electricity that can be used for anything.

Using capacitors in commercial scale processes

Capacitors are most commonly used in many everyday electric circuits and appliances, for example in mobile phones where they help maintain the power supply while the main battery is dead to prevent losing information stored in the memory.

Recent advances in capacitor technology have lead to super capacitors that may have the potential to store energy on a commercial scale.

These super capacitors do not have the conventional dielectric separating the two plates; instead they consist of two plates made up of a sponge like substance known as activated carbon. These plates are separated by a nanometer thick separator and then are immersed in a liquid electrolyte where a current is applied to them. Electrons then build up on the negatively charged plate (as per a traditional capacitor), but as there are free positive ions in the electrolyte solution, a layer of positive ions builds next to this negatively charge plate.

The same occurs at the positive plate, where free negative ions are attracted to this plate and build up around the positive charge. Therefore in an super capacitor each carbon electrode ends up having two layers of charge coating its surface, hence these are sometimes referred to as double layered capacitors.

As the super capacitor is discharged, the negative charge on the plate weakens, which releases the positive ions back into the electrolyte solution and the same happens at the positively charge plate, allowing it to be recharged once again.

How do you make super capacitors hold enough charge for commercial uses?

The capacitance, measured in Farads, is how much electric energy a capacitor will hold given a certain voltage and is based on a few factors which are described below.

• The surface area of the plate coating. In super capacitors the coating they use on the plates is activated carbon, this has an incredibly large surface area, helping to maximise the number of electrons that it can hold. Graphene is now being also being used in supercapacitors; it is made from pure carbon, with atoms arranged in a regular hexagonal pattern but the sheets are only one atom thick. One gram of Graphene has a 1520m² surface area, so this characteristic obviously helps the super capacitor to hold an incredible amount of charge.
• The voltage the capacitor can handle. The higher the voltage the capacitor can handle, the more charge it can hold, so it is key to pick a material that can handle very high voltages.
• The distance by which the two plates are separated. The size of the electrical field generated within the capacitor is inversely proportional to the separation distance. I.e. the smaller the distance the larger the electrical field, hence in supercapacitors the space between the two plates is nanometers thick.

The future of super capacitors

Tesla Motors chief executive Elon Musk has recently come out and said that he believes super capacitors will supercede batteries in the not too distant future. They can be charged in a matter of seconds, and discharged and recharged millions of times without any degradation in performance.

Compared to old style capacitors, a super capacitor has the potential to store about 1500x the amount of electricity, but only about 5% that of a lithium ion battery. However, the ability to release the power is useful, for example if a particular job requires a very short, strong burst of energy, using a capacitor would be better than using a battery.

The hope is that in the coming years, capacitors will become comparable to batteries, so they can hold more charge. Imagine for example, the ability to charge your mobile phone in seconds.

For long-term commercial energy storage, capacitors are still someway off, although even now they can provide a mechanism for dealing with spikes in demand across the grid.

What is compressed air energy storage?

The purpose of compressed air energy storage is to help manage the supply of electricity in the grid. For example when the wind blows a wind turbine will produce power, but this power may be produced when there is no demand for it. At this time it becomes necessary for us to be able to store the electricity, so we can use it when there is a peak in demand. Compressed air energy storage is the second biggest form of energy storage currently behind pumped storage.

Compressed air energy storage involves converting electrical energy into high-pressure compressed air that can be released at a later time to drive a turbine generator to produce electricity. This means it can work along side technologies such as wind turbines to provide and store electricity 24/7. Ideally the compressed air is stored in an existing geographical formation such as a disused hard-rock or salt mine (keeps cost down), rather than producing specialist surface piping, which can be expensive.

How does compressed air energy storage work?

The first compressed air energy storage facility was the E.ON-Kraftwerk’s

290MW plant built in Huntorf, Germany in 1978. This plant was built to help manage grid loads, by storing the electricity as pressurised air when demand was low during the night. When there was peak demand, the compressed air was released to create the electricity, in an effort to lower peak electricity costs.

This plant, which is still maintained as a power back-up installation today, compresses air during times of low demand and stores it in two underground salt caverns. It takes 8 hours to fill both of the caverns at a rate of 108 kg / sec. When electricity is needed, the compressed air is released and heated by combusting natural gas to get the air to expand. This drives a 320MW turbine producing electricity for 2 hours, before the caverns need to be refilled.

Most other compressed air energy storage plants operate along the same principle, although to increase efficiency they are more focussed on retaining the heat associated with compression, which is discussed below.

Increasing the efficiency of compressed air energy storage

One of the major issues with compressed air energy storage is that when you compress air it heats up.  When the electricity is required it needs to be expanded, which requires heat. In addition the cooler the air, the more you can store. Companies are therefore trying to find ways to best store the heat generated during compression, so it can then be used to heat the air for the expansion helping drive more efficiency in the overall process.

There are three types of solutions that can deal with heat build up when the air is initially compressed and are discussed below:

• Adiabatic storage – retains the heat from compression and re-uses this when the air is expanded to produce the power – expected efficiency around 70% (although theoretically 100%)
• Diabetic storage – takes the heat and dissipates it into the atmosphere via heat intercoolers. When the air is released to go through the turbines it needs to be heated – expected efficiency around 70%.
• Isothermal storage – involves using heat exchangers to try to always keep the internal and external temperatures the same, so as the air is compressed heat dissipates into the atmosphere. Once the air is released to drive the turbine and produce the electricity, heat is bought in from the external environment.

New technology is being developed by companies to try and increase the heat retained from the compression process. For example, SustainX from the USA have working on a process to remove the heat by injecting water vapour into the compressed air. The water absorbs the heat which then gets stored and reapplied to the air during the expansion process.

Keeping the pressure up

One of the final issues to overcome for successful CAES revolves around the pressure of the compressed air as it comes out. If the storage facility is full of compressed air, the cavern pressure is higher. Visa versa if cavern is almost empty then the cavern pressure will be low.  Therefore there are two operating modes when storing compressed air in a fixed volume cavern, which are demonstrated in detail below:

• Allow the pressure to change naturally as the air is released, which will mean the turbine creates less electricity as time goes on.
• Control the flow of air out of the cavern, so it releases more of the compressed air at the end to counter the lower pressure. This will ensure constant electricity supply from the turbine / generator.

The latter option is normally used, despite ‘throttling loses’ (the speed at which the air is released from the cavern). This is so there is always a constant store of air driving the turbine, so you can accurately reflect the amount of electricity that the compressed air energy storage facility will be producing.

The future of compressed air energy storage

In the UK, Seamus Garvey, a professor of Dynamics at Nottingham University, is looking at using deep ocean bags known as ‘energy bags’ to fulfil the role of the natural cavities that are used at the moment. The deep water acts as the pressure vessel, and no matter how full the energy bags are, energy should always be the same. In terms of energy storage, Garvey says that with this proposed technology the cost per unit of energy stored is in the order of £1-£10 / kWh, where as comparators such as pumped storage come in at £50 / kWh and electrochemical stores are about £500 / kWh, therefore make this solution very attractive.

It is expected that the UK will need to be able to store about 200GWh of electricity by 2020, to help support the grid that becomes more dependant on intermittent renewable energy sources. Compressed air energy storage could be a valuable tool in allowing us to hit these ambitious targets.

Flywheels as mechanical batteries

Flywheel Energy Storage (FES) is a relatively new concept that is being used to overcome the limitations of intermittent energy supplies, such as Solar PV or Wind Turbines that do not produce electricity 24/7.

A flywheel energy storage system can be described as a mechanical battery, in that it does not create electricity, it simply converts and stores the energy as kinetic energy until it is needed. In a matter of seconds, the electricity can be created from the spinning flywheel making it the ideal solution to help regulate supply in the electrical grid.

It is based on a really old concept and is very similar to an old-fashioned pottery wheel where the potter moves his feet to make the wheel spin. As the potter works, he removes energy from the system, so to keep the wheel spinning; he needs to keep moving his feet.

So how exactly does it work?

A flywheel is a heavy shaft-mounted rotating disc that speeds up when electrical energy is applied to it. When energy is needed, the flywheel is slowed and the kinetic energy is converted back to electrical energy, where it can be transmitted to where it is required.

The energy a flywheel contains is a function of the speed that it is spinning multiplied by the moment of inertia.

The moment of inertia states that the effective mass of a spinning object is not dependant on how much actual mass the spinning object contains. Instead, it is dependant on where the mass is located in relation to the central point that it is rotating around.

For example, if spinning at the same speed, a solid flywheel will store less energy than a flywheel of the same mass that has spokes and its weight situated around the rim of the wheel.

A high moment of inertia is good, but speed of rotation is better!

The speed that the flywheel rotates has a larger effect on the energy stored within it compared to the moment of inertia. If you have a flywheel with a rim weighing 1kg and replace it with a flywheel with a 2kg rim, it has the potential to store double the energy. If you take the original flywheel and double the speed at which it spins, you quadruple the potential energy that it can store.

Innovation of the flywheel

Historically, flywheels have been huge steel structures with the majority of the weight distributed towards the rim of the wheel. However, over the last 30 years, scientific innovation has meant that flywheels can store more energy in less weight and volume, increasing their potential for energy storage. Newer flywheels are made from very strong composite materials and are operated on a bed of near frictionless magnetic bearings housed in a vacuum enclosure. This allows the flywheels to be spun at incredible speeds helping maximise the energy that they can store. In fact NASA scientists have managed to get flywheels to spin in excess of 60,000 revolutions per minute, which is nearly 2.5 times the speed of sound. The amount of kinetic energy that can be stored at this speed makes them ideal for replacing chemical batteries in the future.

There is also potential to use magnetic levitation as a way of prolonging the life of the flywheel energy storage systems. Since there is no friction on a system that is magnetically levitated there will be no wear on the system, so it is thought that these systems could last fifteen years or more as opposed to a chemical battery that may only last five years.

Flywheel energy storage in action

In June 2011, the Beacon Power Corporation completed the company’s first flywheel energy storage plant in Stephentown, New York at a cost of $60m. The plant utilises 200 flywheels spinning at a maximum speed of 16000 rpm to store excess energy and help regulate the supply to the local grid.

On 7^th March 2012, Rockland Capital acquired the assets of the Beacon Power Corporation and put up funding to develop a second 20 MW flywheel regulation plant in Pennsylvania.

Flywheel could be one of the solutions to provide mass scale storage of electricity during excess supply and provide the release of energy during excess demand.

What is pumped storage?

The principles of pumped storage hydropower have been around for many years. Pumped storage accounts for more than 99% of bulk storage capacity worldwide, approximately 127,000MW according to the Electric Power Research Institute (EPRI). In the UK, for example, one of the biggest hydroelectric power stations is at Dinorwig (Wales) which has provided pumped storage since 1984.

How does pumped storage work?

The process requires two reservoirs: one at high altitude and one at low altitude.  When there is low demand for electricity, water is pumped up into the top reservoir through bi-directional turbines, via large water pumps, where it is stored.

When electricity is needed in the grid to meet increased demand, the water is allowed to flow back down through the turbines, which power the generators to create the electricity that can be fed back into the grid.

In the case of Dinorwig, the pump motors are powered by off-peak electricity from the National Grid when it is cheaper overnight because demand is so low. 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.

Getting around the pumped storage topography issue

The problem with traditional hydroelectric pumped storage is that is has limited scope for expansion. You need specific sites that are few and far between. Therefore new forms of pumped storage have to be devised.

One example is the Green Power Island concept devised by the Danish architecture firm Gottlieb Paludan. This concept involves creating a man-made island with a deep reservoir in the middle of it. Wind turbines produce the electricity to drive the pumps that pump the water out of the reservoir in to the sea. When electricity is needed, the water is allowed to re-enter this reservoir driving turbines that power the electricity generators.

The American firm Advanced Rail Energy Storage (ARES) has designed another potential grid-scale pumped storage solution. ARES is the first pumped storage company that does not rely on water. Instead it is a rail-based technology that stores energy by moving a heavy mass ‘train’ against the force of gravity. When the electricity is required, the train uses the stored gravitational potential energy to return to its original position. This motion drives turbines that produce energy via generators.

ARES is aiming to produce a wide range of energy storage facilities from 100MW to 3GW. A 3 GW system has the potential to store 24GWh of energy. In real terms, if it were implemented in the UK it would be able to power over five million homes for eight hours. Another advantage of this water-free pumped storage solution is that it is highly efficient at 85% (the ratio of energy in to energy out).

Could pumped storage be a viable energy storage technique?

In conclusion, pumped storage has already a proved to be a solution to helping countries meet peak demand. The Dinorwig power plant in Wales has been in operation now for over 25 years helping manage demand in a highly reactive way; in just 12 seconds the plant can switch from being fully shut down to operating at full capacity. To take this a step further, building wind turbines, solar PV farms and tidal energy near Dinorwig is one way to replace traditional generation technologies and connect renewables with energy storage.

New concepts are constantly being developed to remove the need to find particular topological features for pumped storage, thereby helping to open this energy storage solution to all corners of the globe.

Windstalker – another way to harness wind

Windstalker is an alternative energy concept designed by Atelier DNA that recently took second place in the Land Art Generator competition. Like wind turbines, the Windstalker installation harnesses wind to produce power, however it does so using a very different method. Essentially it consists of extremely tall and thin structures that sway in the wind, and this kinetic movement can be harnessed to produce the electricity.

In this particular design, there are 1203 of these stalks spaced very close to one another, giving the appearance of a field of wheat swaying in the wind (albeit on a much larger scale!). Each of the stalks is 55 metres in height, and despite being 0.3m diameter at the base taper to only 5cm at the top. The stalks themselves are made up of carbon fibre reinforced resin poles making them extremely strong and are anchored to the ground with concrete bases approximately 10 to 20m in diameter, which define the spacing achievable from one stalk to the next.

How does Windstalker generate electricity?

The electricity itself is produced using piezoelectric ceramic disks, which are stacked upon one another within the stalk, with electodes sitting between them. Piezoelctric substances produce an electric charge in response to applied mechanical stress, so when the wind hits the Windstalker stalks, it causes compression of the disks generating a electrical current through the electrodes, which travels down to a torque generator located in the base of the stalks which produces the electricity that can then be used by consumers.

Like Wind Turbines, the wind stalks will only produce electricity when the wind is blowing and the stalks are moving, therefore electricity production is not constant. In an effort to compensate for this, beneath the Windstalker installation lies an energy storage mechanism that consists of two very large chambers which sit one upon the other. When the wind is blowing and electricity is being produced, some of this power is used to drive water pumps which pump water from the bottom chamber into the upper chamber. When the wind stops blowing, the water is allowed to flow through the pump in the opposite direction, from the upper chamber into the lower chamber, driving the turbine in the pump which connected to a generator can produce electricity, ensuring a more constant source of power.

Windstalker and current commercial proposition

The Windstalker project currently is purely conceptual, but based on technologies currently available to the scientific community.  The estimated power output from an individual stalk is considerably less than a current wind turbine; however the stalks can be positioned much closer to one another, so the actual output per area unit is comparable. In addition this technology would have the benefit of lower noise pollution, less danger to wildlife (wind turbines are a real threat to birdlife), while still producing renewable energy with zero emissions. It will be interesting to see in the coming years whether the Windstalker energy concept is bought to life, and whether it will one day sit side by side with existing proven green technologies.

What is VIVACE?

VIVACE stands for Vortex Induced Vibration Aquatic Clean Energy, and is a technology used to extract energy from flowing water currents.

Vortex Induced Vibrations (VIV) are a physical phenomenon resulting from vortices forming and shedding on the downstream side of a bluff body (e.g a bridge support) in a current. The shredding of the vortices alternates from side to side creating vibrations. For decades, scientists and engineers have worked to try to prevent VIV damaging offshore structures such as oil platforms and bridges

In 2005, Professor Michael Bernistas of the University of Michigan turned this preventive research on its head, trying to maximise VIV and developing a system for harnessing its power. In doing so, he produced a converter unlike any existing technology currently in use, instead of turbines or propellers; the VIVACE converter uses cylinders that move up and down in the water due to the VIV. As these cylinders move vertically in their runners, they move magnets along a coil producing DC current.

VIVACE is the first system that can harness water currents under 2knots, where as conventional turbines and water mills require an average water speed of 5-6knots to operate efficiently. The majority of the earth’s currents travel under 3knots, so this technology is suitable to be situated worldwide and it has speculated that if we could harness just 0.1% of the energy in the ocean, it would support the energy needs of 15 billion people.

Vortex Hydro Energy has exclusive license to commercialise the hydrokinetic power generating device, and is currently running tests in the Detroit River of various types of system.

What are solar updraft towers?

Solar updraft towers use solar energy from the sun to drive turbines, which in turn create electricity. The method that these towers use to generate the power is very different to both solar photovoltaic and concentrated solar power plants.

The solar updraft towers uses the very simple premise that hot air rises as their basis for energy production. Essentially they consist of 3 parts, the first is a massive solar collection area (potentially over 1km x 1km), where the sun hits a greenhouse type structure, heating the air underneath it, and trapping it in.

In the centre of the collect area is a large diameter concrete chimney structure, which vents the hot air into the atmosphere (as the hot air rises). As the hot air moves from the solar collection area to the chimney structure, it drives the third element of the solar updraft tower, the electricity producing turbines, these are either situated around the base of the chimney, or actually in a horizontal plane within the chimney itself.

The 2 primary factors in solar updraft towers

There are two factors that are critical for successful operation of a solar updraft tower. The first is the size of the collection area; put simply, the bigger, the better. The more air that gets heated in the greenhouse collection area, the larger the volume of warm air that will travel up the chimney.

The second factor is the chimney height, when again bigger is better (750m plus). The higher the chimney, the greater the pressure generated by the temperature differences, resulting in a larger stack effect. The stack effect relates to movement of hot air through the tower, so the higher the tower, the more electricity can be produced.

Practicality of solar updraft towers

A Spanish man called Isidoro Cabanyes first proposed solar updraft towers in 1903, however it was not until 1982 that a small scale solar updraft tower was built south of Madrid. This test power station was operational for 8 years, before the tower collapsed due to a storm as the result of inexpensive materials used in it’s production. The chimney was 195m high, and the collection area was approximately 11 acres, giving the plant a maximum electrical output of 50kW.

It really then became a forgotten technology until about 5 years ago when numerous proposals were put forward to build much larger solar updraft towers than the Spanish test facility. One of the major issues with this type of solar power station is that for them to be a worthwhile investment, a large collection area is required. This makes it unsuitable for areas that have high cost per acre.

In addition there are high associated initial capital costs for the construction of these plants. When compared to solar photovoltaic plants and concentrated solar power plants, these solar updraft plants also are incredibly inefficient, only capturing a fraction of the solar energy that hits the ground.

Despite this, in October 2010, Enviromission announced plans to build 2 200MW solar updraft towers in Western Arizona, which have the potential to supply 100,000 homes with electricity.

There are also additional benefits when comparing the updraft towers to traditional solar photovoltaic and concentrated solar power stations. In addition to creating free clean electricity supply, unlike other solar sources that are intermittent, relying on the sun shining to produce electricity, solar updraft towers can produce power 24/7 if special materials are used under the collection canopy that reduce the heat slowly through the night.

In addition underneath the collection area canopy, condensation created at night allows the soil to be used for arable land, enlivening potentially otherwise barren desert. In addition there is sufficient clearance between the canopy of the collection area and the ground allowing farming equipment to move freely.

Finally if the towers were associated with air filters (potentially carbon dioxide), this technology could also act as a CO₂ scrubber (a CCS Technology) potentially helping to avert global warming.

The future of solar updraft towers

Solar updraft towers certainly have the potential to become a useful tool to help combat climate change. If production costs can be reduced, these would be ideal in third world countries where there is lots of cheap space to build the plants.

There are also patented designs that replace the large concrete chimney with a low cost fabric designs held in position using successive tubular balloons filled with lighter than air gas (such as helium). These would make the plants far cheaper to produce, although these have not been tested on a commercial scale.

A lot will depend of the success of Enviromission’s two planned solar updraft plants in Arizona, which will be completed in the next couple of years.

The sun and solar energy from space

Our sun is the largest known energy source in the universe. In the vicinity around the earth, each m² receives 1.4KW of solar radiation, however as this solar radiation travels through the atmosphere and hits the ground, due to day-night cycles, summer-winter cycles and weather, each m² receives just 250W.

If we were able to harness a single KM wide band around the earth in geosynchronous earth orbit (the height at which a satellite would sit), it would receive approximately the same solar energy in one year as the total amount of energy contained in the combined recoverable oil reserves on earth today (~211 Terawatt years compared to ~250 Terawatt years).

How does space-based solar power work?

Space-based solar power captures sunlight in orbit where it is constant and stronger than on earth. This then gets converted to coherent radiation and beamed down to a receiver on earth. The typical design for this would be a satellite sitting in geostationary orbit with kilometres² of photovoltaic arrays situated either side capturing the sunlight producing the electricity. This would then be converted to radio frequencies that are best suited to atmospheric transmission and beamed down to a reference signal on earth, where the beam would picked up by a rectifying antenna and converted into electricity for the grid, delivering approx 5-10GW of electrical power to the grid.

Space-based solar power does not require any scientific breakthroughs or new physics to become reality. Since the idea was first put forward in 1968 by the Nasa engineer Peter Glaser, these breakthroughs have taken place, and all of the technologies involved have come on leaps and bounds. The international space station currently has solar panels the size of football pitches powering it, as do most satellites currently orbiting above the earth.

Space-based solar power is currently being held back as a viable energy solution by the high cost to orbit. It could not be achieved without safe, frequent (daily or weekly), cheap and reliable access to space, and the current lack of this makes it prohibitively expensive.

What are piezoelectric materials?

Piezoelectric materials are materials that produce an electric current when they are placed under mechanical stress. The piezoelectric process is also reversible, so if you apply an electric current to these materials, they will actually change shape slightly (a maximum of 4%).

There are several materials that we have known for some time that posses piezoelectric properties, including bone, proteins, crystals (e.g. quartz) and ceramics (e.g. lead zirconate titanate).

However, in May 2012, it was announced that University of California Berkeley lab scientists have found a mechanism of harnessing piezoelectricity from viruses. This is the first time a biological material has been used to make piezoelectricity.

Why are piezoelectric materials of interest?

Imagine walking down the street and charging your phone as you walk, charging your laptop by typing, or powering a nightclub by dancing on a piezoelectric floor! The concept of piezoelectricity has been around since the 1880s and was discovered by Jacques and Pierre Currie. Despite already being used in things like lighters to create the spark that ignites the gas, using it as an everyday energy source is still a long way off.

Issues with current piezoelectric materials

There are 3 issues that we are currently faced with in trying to tap into piezoelectricity as a viable electricity production method:

• The major issue one is that the quantity of electricity produced is so small, so unless vast installations were set up, it simply would not have the strength to power our latest gadgets.
• The current is only produced when there is mechanical stress being applied, so as soon as you stop compressing the material, there is no charge produced.
• The final issue is that up to now, many of the starting products needed to produce the piezoelectric materials are toxic and difficult to work with.

Why newly identified viral piezoelectric material could be the answer

There are many reasons why this finding could revolutionise the piezoelectric field. Firstly, viruses replicate incredibly quickly, producing millions of identical viruses within hours, so your supply is potentially limitless. In addition, as it is a virus, scientists can relatively easily genetically engineer it, thereby improving its piezoelectric characteristics. The virus itself is shaped as a rod, so when many come into contact, they naturally orient themselves into a amazingly organised film.

If you look at the Windstalker technology, you will see that the engineers behind it looked at ceramic piezoelectric materials being positioned within the wind stalks to harness the wind’s energy. This new research completed by the Berkeley lab, could make this potential technology more viable, as there is now a cheaper source of the piezoelectric material.

The future of piezoelectricity

Piezoelectricity is an exciting field of Nanotechnology, and there are already tests being run outside labs to try and harness this form of power. In many places including Japan’s subway, dance floors across the world and football stadiums, engineers have already put in place piezoelectric floors that use the high volume of footfall to decrease their demand for electricity from the grid. With a bit of luck in the years to come, piezoelecticty will become another weapon which we can use to reduce our reliance on fossil fuels and to derive the energy we need.