Clean Energy Solutions

Page first edition 12/03/2009, last updated 31/10/2024.

Background

December 29 2007 was a turning point in my life. Up until that day I had agreed with the almost universally held belief that a world powered solely by clean renewable energy systems would be incredibly difficult to achieve. Being a holiday, and having nothing planned for the day, I relaxed and contemplated the planet and its future. Suddenly I realised that floating islands covering large areas of the sea are the way to go to generate most of our energy. They could also provide much of the food and other agricultural products that are now produced on land. Forests, and other priceless wild areas, are being cleared to make way for farms at a rate that appals anyone with a conscience.  Floating energy islands covering hundreds of square miles, or thousands of square kilometers could solve many severe problems we face today.

Much of the sea has little life in it - as little as in a desert. This is because essential nutrients like iron and phosphorus are missing.  Country sized floating islands could turn some of that sea surface from being almost lifeless into highly productive farms producing energy, food, fuel, charcoal and other products. Using the technology I started to visualize that special day during the Christmas break we could do it all at a reasonable cost, with negligible pollution, and safely.

Every second of every day the Sun pours six thousand times more energy onto our planet than the total of what we use. We do not have an energy crisis as such but an energy conversion crisis. Almost 80% of that energy falls on the sea. We therefore need to find ways to make islands that can capture about 0.1% of it.

The energy density in renewable sources is low and variable, so building systems to collect it can look daunting. However, most of the expense is in the early stages of development and having taken the trouble to establish renewable energy technology the running costs are low; and the pollution is negligible. Once the volume of production of renewable energy systems reaches a critical level the total lifetime cost of energy (LCOE) will drop below that of fossil fuel systems. Once that happens the uptake rate will explode and everyone will benefit as the pollution from our dirty past clears away.

If people had a more optimistic outlook about the prospect for clean energy maybe they would more readily embrace the needed changes. Optimism is needed to help overcome the technical, social and political challenges we face.

Energy island fundamentals

There are numerous stories of wave energy machines being smashed to pieces in storms. Wind turbines are also often damaged by high winds despite the industry spending much of their time designing storm protection into their products. Anything we make to harvest wind and wave energy needs to be huge because the energy density is normally low. The problem is that sometimes the weather flares up and the machines have to withstand forces at least 100 times greater than they usually do. Building in extreme weather protection multiplies the cost and complexity, but it is essential, and the designers of energy islands need to take this into consideration.

Solar power has by far the greatest potential out to sea. Although solar panels do not need protection against the Sun becoming too strong they do need to be mounted on supports that are storm resistant. By building huge floating islands that harvest wave, wind and solar energy we can achieve storm protection at a practical price. Most of the solar panels can be protected by putting them within a tough rim of wind and wave energy harvesting systems.

To construct a building a scaffold, or lattice-work of poles and platforms, is first erected. Similar low density structures have important advantages for energy island construction. Strong winds and large waves go through them without creating huge forces. By building high a light structure can bridge the huge distances between the crests of storm waves (several hundred metres). The lattice structure that is both wide and long (many kilometers) is totally stable so the vast majority of the island can be well above the sea. This has critical advantages for avoiding corrosion and fouling.

Initially islands will be tethered and able to feed electricity directly to land. As the islands get bigger this will become impractical and they will have to be free floating. They will then have to get their energy to land by manufacturing a transportable fuel. This could be dried algae, refined metal, desalinated water, or a liquid fuel such as methanol or ammonia.

Manufacturing fuel adds costs and reduces efficiency but a free floating island pulled around by wind energy has big advantages. Using long-range weather forecasts it can avoid storms. It can also go where the Sun is strongest. Huge areas of sea to the west of Southern Africa and South America receive very little rain and would be ideal for huge floating solar arrays. www.physicalgeography.net/fundamentals/images/GPCP_ave_annual_1980_2004.gif

Some power figures

The Sun continuously pours 174 000 TW onto our planet and of this 96 000 TW gets through our atmosphere to hit the Earth's surface. These figures may not be so meaningful on their own but can be divided by the population of the world to get a personalized result. Assuming 7 billion people at the time of writing we see that 13 714 kW per person gets to ground level. That is like a million 13 watt light bulbs burning all the time for every person. Considering that humanity's total energy usage is about 16 TW or 2.2 kW per person we can see that we only need to use a tiny proportion of the Sun's energy to supply all our needs (1/6000^th).

Another way to analyse the figures is to consider that the intensity of the sunlight we receive averages over night and day up to 250W/m². Assuming a conversion efficiency of solar collectors of 12% that means on average we need about 75m²  per person to supply all our energy needs. Mark Z. Jacobson has suggested that if all suitable roofs had photovoltaic (PV) panels installed on them we could generate 6% of our total energy requirement. He suggest another 14% could come from large-scale PV and 20% from concentrated solar power. He did not consider floating energy islands which could easily provide 100% of our power.

The oceans cover just over 70% of our planet's area (361 million km²). For some strange reason most of the land surface is north of the tropics. The tropics receive the most power from the sun yet most of it is sea. Therefore about 80% of the Sun's energy falls on the sea. Using efficient photovoltaic (PV) panels we would only need to cover 0.1% of it to generate the 16 TW humanity presently uses. Transmitting electricity over the vast distances to where we need it is a challenge so conversion to a high energy density fuel makes sense. Algae farming is one idea. Chemical facilities that convert water and the carbon dioxide in the air into a liquid fuel is another.

Iron and phosphorus limitations make the open oceans remarkably unproductive. The biomass is formed at rates lower than on Arctic tundra but higher than in desert scrub. Measured as the energy contained within the biomass growth rates are approximately 2.5, 1.5 and 1 MJ/m²/yr (0.08, 0.05 and 0.03 W/m²). www.globalchange.umich.edu/globalchange1/current/lectures/kling/energyflow/energyflow.html
The deficiency of critical elements could fairly easily be overcome because the concentrations needed are small. The total biological productivity of the oceans exceeds that of one of the most productive environments - the rain forests. 190 vs 180 billion kcal/yr (90 TW vs 85 TW). Artificial floating energy islands with imported nutrients could possibly match the specific productivity of the rain forests:- 40 MJ/m²/yr or 1.27 W/m². That means we would need 12 million km² of algae farms to get 16 TW of algae fuel. That is 3.3% of the total sea surface. The total area of arable land is already 14 million km² so doing almost as much again at sea is humanly possible. Photosynthesis is not very efficient (3% at best) so artificial fuels will also be important.

People often look for a silver bullet - a technology that will single handedly solve all our energy problems. We face such huge problems, and action is needed so urgently, that we need to throw all our efforts into developing all sensible renewable energy options. In places with low average wind speeds wind turbines are a waste of money. Solar panels need good sun and geothermal needs hot rocks at an accessible depth, so to supply the whole world we need a mix of many technologies. The energy islands I envisage will be complex systems employing wave, wind, solar and thermal energy using a wide range of technologies. They could come to dominate the energy industry, but land based technologies will continue to be important. Measures to conserve energy, and use it much more efficiently, have been shown to give excellent returns on investment, so they are also vital.

Below some promising technologies are discussed.

Solar

The recent drop in the price of PV panels has been remarkable. We have already reached the situation where the LCOE of PV is less than that of diesel generators in most of the world. The industry is booming and that boom is sure to continue for some time. New thin film PV technologies are being developed that will pay back the energy used to manufacture them in well under the 3 years often quoted for modern panels.

Large solar thermal generators are more efficient than any PV, but facilities built so far have to be situated in deserts to make economic and ecological sense. They use mirrors to concentrate the sun onto a heat engine, and track the sun so that the engine is always supplied with concentrated light.

The desert location would often require the transmission of the power over great distances but that is possible using high voltage DC (HVDC). The construction of a global HVDC network (the so-called Super-grid) is technically possible and economically viable even though it would require a large investment and cooperation between many countries.

Concentrated solar generators require stability to maintain focused so although the inside of energy islands might be able to meet the requirements, PV is likely to be the dominant technology at sea. My island concept keeps the panels well above the water, mainly to avoid physical damage from large waves, but it also reduces corrosion worries. The cells can be encased in glass on both sides so those worries are not great anyway.

Biochar

Because there is more land in the northern hemisphere than the south there is a dip in the atmosphere's CO₂ concentration every Northern spring and summer. It then rises again every Northern autumn and winter. The plants grow in summer and capture carbon from the air and then after the autumn (fall) much of it is released again as the leaves rot and the animals continue to eat. We can capture that carbon by charring waste biomass before it rots. Some biological decay needs to be allowed to maintain soil fertility but there is still enough waste biomass to make a substantial difference. The main advantages are:

1. The charring process can supply us with energy.
2. Once charred the fungi, bacteria etc. responsible for the rotting process cannot oxidise the charcoal.
3. Charcoal ploughed into the ground is an excellent soil enhancer. It stays there for many centuries benefiting both the soil and the atmosphere.

Many are working on biochar production systems, but none have attracted enough funding to develop anything that is ready for wide scale adoption. I know it could be done if the resources were applied, because the fundamental physics clearly show it is possible, but the technical challenges are significant.

Algae

For a while into the future we are likely to need hydrocarbon fuels to power aircraft. No one, to my knowledge, has come close to demonstrated a viable alternative. Hydrocarbons will also be needed to some extent for surface transport. Attempts so far to supply this hydrocarbon fuel from biomass have not had good publicity. The biofuels have been blamed for increasing deforestation and pushing up the price of food. We urgently need to step back, rethink our approach, and do some more research.

Algae grows very fast in the right conditions and can be made to produce oils that need little processing to turn them into fuels. There is ample space on our seas, using floating islands, to grow all the algae we would need. Algae farming has been criticised for a number of problems such as water and energy consumption. Energy islands can solve these issues. Many species of algae live in the sea so that can solve the water problem. Power from the waves,wind and sun can provide the power to aerate the algae, then to filter it off and dry it before processing into fuel. A holistic solution that brings many technologies together is required.

Wind

A significant proportion of the Sun's energy is turned into wind. It is estimated that at the height of modern large turbines the total resource is up to 100 TW (14 kW per person). Wind gets much stronger at higher altitudes so a technology that could tap into this resource could produce many times more power. The estimated usable resource increases to 870 TW or more. Kite based wind interceptors mounted on floating generators far out to sea could provide all the power we could ever want. This system would save us from having to cover our terrestrial environment with controversial turbines. Once this technology gets established it will reduce the price of energy, not increase it. This is because kites use far less material than turbines so the system cost will drop dramatically as soon as mass production starts.

Large terrestrial wind turbines have already reached the stage where they pay back the cash invested in their construction before they fall apart. If the price of oil shoots up again investors will make a fat profit from them. Typically they compensate for the carbon used to make and install them within 3 months. Because of this demonstrated success the industry was growing at 30% p.a. until the credit crunch slowed things down.

The smaller the turbine the more economical in can be in the use of materials. The difficulty is that their price is dominated by the labour costs of their design, construction, installation and maintenance. If someone with enough money to start mass-producing small turbines was brave enough to go ahead their price would come way down. The lower specific mass and economy of scale could make them a bigger success than big turbines. Kites have an even lower mass so ultimately they will dominate once the complex issue of automating them has been solved.

Kites are already used by Skysails to tow ships and reduced their fuel consumption. They have the great advantage over sails that the force applied to the ship is much lower so the vessel does not keel over when the wind picks up. Kites can also reach the stronger winds way above the reach of sails. In the fairly near future improved kites and control systems could provide ships with nearly all their motive energy. Mobile energy islands will also use them to position themselves.

A criticism frequently levelled against wind power is that it is variable. This means fossil fuelled generators are kept running just in case they are needed to quickly increase their power output, and this consumes extra fuel. It certainly does not waste enough to ever make wind turbines a burden on our total emissions but it is an issue that needs addressing. Energy storage is one solution and that is discussed below. Better prediction of the wind is another, and organisations such as the National Center for Atmospheric Research (NCAR) have announced some promising progress. The developing smart grid initiatives that help match demand with supply will also make an important contribution.

The Wind Energy sub-page covers up-coming wind power technology in more detail.

Tidal and ocean current

Turbines, or water-kites, in the sea can generate power from the motion of the water caused by tides or currents. The main problem I foresee with ocean energy will be getting consensus that the disruption caused to the local environment is worth the value of the energy generated. One company with an interesting water-kite concept is Minesto.

A very interesting extension of the basic idea is to build what have also been called energy islands (except these do not float). Essentially a long dam wall is built to enclose a significant area of ocean, so sea dam would be a better name. A set of turbines that act as either generators or pumps are installed in the wall. When there is a surplus of energy the turbines pump water out of the dam. When there is a shortage the turbines allow water back in and generate power from the level drop. Using a more complex system of staged dams and prediction of energy usage and supply, the scheme could work with the tides so that tidal movement adds to the total energy generated.

Wave energy

Wind blowing over thousands of miles of ocean creates the most concentrated of the renewable energy sources; waves. In the roughest oceans the power averages about 100 kW per metre. That means that a 10 km long collector could potentially generate the same power as a typical fossil fuel power station which is approaching 1 GW.

A critical feature of a wave machine is the ability to absorb the energy from small and medium waves but to shrug off the terrific impact of big waves. My proposal is to support the islands on thousands or millions of spherical floats. Each float will be attached to an open-framed or lattice-work support structure. These structures will be be used to press the floats into the sea from above. Each float and its support structure will move in response to the sea below. The relative motion of each float will be used to generate energy. The support structures will be designed to offer minimum resistance to large waves that pass over the floats so that the force on the floats can never exceed the designed maximum value.

On the outside of the islands the floats and their support structures will be free to follow the waves. Further inside the islands far more stable conditions will be created by connecting the floats to a more rigid lattice structure. On top of this lattice support it will be possible to build houses, airports, factories, and farms.

The floats will be small enough so that replacing damaged ones will be easy. Mass producing millions of them will get the costs right down. The safety of island residents will also benefit. It is well recognized that multi-hulled ships are safer than single hulled ones. An island with a million hulls will be difficult to sink.  It will also be possible to create a very stable inner area that will be almost totally isolated from the motion of the sea below.

Geothermal

The uranium and other radioactive elements in the granite, and similar rocks, deep in the earth creates a valuable heat resource. Their depth in the earth means they are well insulated so they are very hot. Deep boreholes down to these rocks are used to create super-heated steam. This steam is used for heating or to generate power. Geothermal is limited both by the areas in the world with a viable resource and by its total capacity. It is therefore best exploited in combination with the resources listed above. When the sun, the wind and the waves are not producing enough power the geothermal can be turned on. When it is not needed it is turned off and the heat is allowed to build up again.

The word Geothermal is sometimes incorrectly used to describe ground source heat pumps (GSHP). Both involve pipes in the ground but with GSHP they are much nearer the surface. GSHP uses a heat pump that requires an external energy source. That energy input is amplified by taking advantage of the high thermal mass of the earth. Geothermal systems output energy and because of the depth of the boreholes they only make sense for systems that can supply a whole town, or city. GSHP is suitable for single homes and together with air source heat pumps they are growing rapidly in popularity because of their ability to save energy.

OTEC

OTEC stands for ocean temperature (or thermal) energy conversion. In deep oceans in the tropics the water gets rapidly colder the deeper it is. By pumping large quantities of water up from the deep ocean to the surface we can use the temperature difference between that and the surface waters to generate power. To be viable the process would have to be done on a very large scale. Developing the process is therefore risky. As with geothermal energy the resource is limited. If it has a place in our future it is likely to be as a topping-up supply, as with geothermal.

It has interesting implications for the fertilisation of the surface ocean because the deep ocean contains some of the nutrients that are scarce near the surface. The energy islands I envisage could use OTEC to draw up nutrients from deep ocean beds. They can then be used to grow algae for energy, and fish for food. 

Energy efficiency

A huge proportion of the energy we use is for directly, or indirectly, keeping our indoor environment at a comfortable temperature. When it is cold outside we turn on the heaters and when it is hot we turn on the air conditioners. We also use many energy consuming gadgets indoors and these contribute to the heating when cold and add to the load on the air conditioners when hot. In the UK nearly 50% of the total energy used is a contribution to this process. It is therefore by far the most important single category of our carbon footprint.

The ridiculous thing is that it does not have to be this way. Addressing the issue would save us a lot of money with pay-back times sometimes being as short as a few months. That is before considering the huge ecological benefits. The fact that we have done so little for so long is a damning reflection on our culture.

The technology for building passive houses that require no extra energy for heating or cooling has been demonstrated in many climates. The only thing that is required is a sufficient shock to make us change the way we build houses.

Considering how slowly existing houses are replaced with new ones it is clear that most effort needs to go into fixing existing houses to make them better insulated. This can be expensive and inconvenient but more could be done if the motivation was high enough. Loft and cavity wall insulation is widely promoted and it helps. Ideas like insulating wall plaster and cheap external cladding need more support.

Besides indoor temperature control there are other big energy sinks that need attention. In the previous decade there was a big push to replace incandescent light bulbs with fluorescent ones. These contain mercury so it is fantastic news that LED lights, which are even more efficient, have made such great progress. Electrifying our transport is also finally starting to progress. I cover this in more detail in my Ideal hybrid car page.

Nuclear

I am not a fan of nuclear power for several reasons.

1. Fuel for nuclear fission is not truly renewable. Whether we use uranium or thorium there is a finite supply.
2. Fission produces some incredibly nasty waste products and I have not yet heard of a satisfactory method for dealing with them.
3. In the early days nuclear power was over-hyped because of its military importance. This has created a legacy of mistrust and there is still a big doubt that it makes economic sense to build new fission reactors. Besides, we would not need them if we embrace the solar and other clean energy sources mentioned above.
4. Nuclear fusion is a long way from being practical. The sun does that for us anyway so why not just use the energy it sends us every day without fail?

I am not saying fusion research should stop because we are learning valuable information from the effort but it should be kept in perspective so that sufficient money can be spent on renewable energy systems that will produce quicker results. The same applies to fission because a certain number of fission reactors are a very valuable resource. One example is that they supply a range of radioactive isotopes crucial for many branches of science. However, it needs to be kept in balance because nuclear presently does not make a lot of sense for pure energy supply and sustainability reasons.

Recently publicity about liquid fluoride thorium reactors (LFTR) has boomed. The technology has some very important advantages such as increased safety. It is much harder to use a LFTR energy program for weapons. It also offers a solution to the recent crisis with the supply of rare earth metals. Deposits of rare earths frequently also contain thorium.The metal makes an excellent solid ion conductor but radiation fears prevent its wide-spread use for that, or anything else, so it has very little value at the moment. Using it in LFTRs would help solve the rare earth metals crisis.

Fuel cells

Having spent many years doing fuel cell research I have become very familiar with their advantages and problems. When I first started hardly anyone knew what they were. Interest in them has since exploded because in principle there is no more efficient way to turn fuel into electricity. Some major problems include

1. Efficiency drops rapidly as power output increases (in most types, but in types where this is not true efficiency is always low).
2. The cost of construction has been incredibly difficult to decrease to a level where they compete with existing technology.
3. Very pure fuel is required for low temperature types.
4. It is difficult to find an efficient way to make fuel for them without using fossil fuels.

Some FC types still offer advantages that other technologies struggle to match so there will definitely be a place for them in the future energy mix. However, I no longer believe that they will be the major contributor to the future of clean energy.

To take best advantage of them we need to take advantage of the fact that most types are far more efficient when they are delivering a small proportion of their maximum power. These types should therefore be built into applications where full power is only occasionally needed but trickle power is needed for long periods. I write more about this in Ideal hybrid car .

Energy storage

Two of the most promising renewable energy sources, solar and wind, suffer severe intermittency. Because we do not yet have an economical method for storing electrical energy they are often dismissed. This is tragic because solutions become obvious if we look at the whole picture with an open mind. More detail is discussed at Energy Storage Solutions

Sequestration

Numerous schemes for pulling CO₂ out of the air are being investigated. The gas is being pumped into oil wells to help extract the last dregs of oil out of the ground. There is talk of making it react with silicate rocks, and so on.

Low CO₂ cements, and other building materials, are also being investigated. Cement is made by using carbonaceous fuel and CO₂ is driven out of limestone. By starting with silicates instead of limestone we could drastically cut the carbon footprint of the building industry. Calix also looked at calcining the limestone first before feeding the calcium oxide to the cement kiln. The calcination step allows them to capture pure CO₂.

Reviewing this page 15 years after first writing it this is the only section that needed a major change. My work with Cambridge Carbon Capture Ltd between 2022 and 2024 has produced some very interesting results that hold huge promise. A new page all about that is planned.

In my next essay

I start explaining why it is so critically urgent to invest in every clean energy idea mentioned above, and more; Global warming