Renewable Energy and Alternative Energy Sources
How We Get Energy from the Sun, Earth and Moon
|Several Energy Suppliers offer consumers a part in the greening
of society by deriving their energies (at least in part) from renewable
or alternative sources and in some cases they will support environmentally friendly projects. The terms renewable and alternative do not necessarily
mean the same thing but the distinction is blurred. There are two main
objectives in this context, the most obvious of which is to reduce the
net emission of greenhouse gases, especially carbon. The other is that
the resources should remain constant and not run out in any foreseeable
'Renewable' energy implies that it is derived from a source which is automatically replenished or one that is effectively infinite so that it is not depleted as it is used. The term 'Alternative' refers to energy sources which could replace coal, traditional gas and oil or their close derivatives, all of which increase the atmospheric carbon when burned as fuel.
Coal, Traditional Gas and Oil are not renewable because, although the fields may last for generations their time span is quite finite and we are aware that they will run out eventually.
Care has to be taken when using the term alternative energy. For example electricity as a power source for cars would normally be thought of as alternative, but if you have to charge the batteries from the mains and the power station that supplies your electricity is coal fired then that is not a renewable source (neither is it strictly alternative). Similarly Ethanol as an alternative fuel to petrol (gasoline) could be derived from petroleum or from energy crops; if the former it is not renewable but from crops it is. If you burn logs, do you also plant trees (or use timber from the waste stream)? If so, that's not bad, but otherwise you contribute to global warming. There are many other examples.
It is evident why the terms alternative and renewable are often considered to be interchangeable but why the concepts are sometimes ambiguous. However, we feel that the term 'renewable' is preferable and any sources that are renewable are also alternative.
Basically, renewables derive their existence from the sun with a little help from the moon, and until the sun goes out and the moon falls the associated energies will always be there for us to use.
|What are the main Renewable Energies?
We identify most of the main sources below with a brief resumé:
[Note: to access Reference articles for more information on each topic, scroll down and click on the headings.]
The sun causes differential heating of the earths surface, hence wind turbines.
There are several mechanisms:
1 Wind causes waves on the sea making wave-power generators practical.
2 The sun and moon cause tides which facilitate barrage hydro-electric plants and tidal-current generation.
3 The sun evaporates water, rain falls, streams flow, hence hydro-electricity.
Also several mechanisms (including for example):
1 Passive: buildings are constructed to trap the heat.
2 Active: solar constructions eg on roofs capture heat in water storage systems.
3 Photovoltaic (PV) Cells: when suitably positioned convert sunlight to electricity.
4 Hydrogen gas can be produced from water using the sun's energy (in hot climates).
5 Electricity can be generated using concentrators and Stirling engines (in hot climates).
6 Provides energy to crops.
|And a Few Earthly Sources:
(A disparate collection which we feel to be relevant)
This is highly technical in the detail but there seem to be two different mechanisms.
1 Heat may be collected from hot rocks deep underground in mother earth. This is clean and offers very large capacity but there are restricted opportunities since it is dependent on geographical location. As far as we know the UK does not have any potential for this technique but there are many long standing, proven installations elsewhere.
2 An alternative method, more suited to smaller and more diverse installations, is to bury a heat exchanging network of pipes at relatively shallow depths. The normal sun's radiation combined with the storage capacity of the ground enables heat to be extracted on a renewable basis. This method uses heat pumps and offers an additional advantage in that it can operate in reverse so that in hot conditions it can be used for cooling. The UK has domestic schemes which operate using this technology but believe that installation depends on community negotiation rather than individual dwellings.
Hmmmm! what can we say. It has potential (and is used by several nations including the UK, now) because it doesn't emit carbon but disposing of the toxic and dangerous waste seems to be an insoluble problem. At the time of drafting this article we concluded that nuclear power was not likely to be developed in the UK. Unfortunately, since then, up to 2007, we see evidence that the UK government has changed its mind. Even based on the history of its pernicious presence, nuclear power does not seem to warrant a place in our society. In view of the potential for terrorist activities and especially since 11 September 2001 (the Twin Towers terrorist attack), a possible strategy to develop it seems to us to be incomprehensible.
|Biomass and Coppicing; an energy crop (See
also Biodiesel and Ethanol below)
These are plants (eg fast growing trees, seed or bean plants) which are grown specifically as a source for fuel, absorbing energy from the sun and carbon from the atmosphere. After suitable treatment to produce the usable fuel they are burned and in the process release carbon compounds. The argument is that as long as the crops are continually replanted, the carbon sinking during the growth stage compensates for the emissions. When correctly managed it is a fairly clean, renewable energy source but it not entirely free from environmental problems such as a reduction in natural diversity and displacement of food sources. Log burners and stoves are fairly common and provided the logs (and other clean wood) are taken from renewed sources or the waste stream they can be classed as environmentally friendly and have the potential to be very cheap to operate. Wood pellets are becoming increasingly popular in the UK and have a track record in Germany, Austria and Scandinavia. The boilers are relatively expensive and since the pellets are manufactured the fuel has a cost. Nevertheless the fuel is significantly cheaper than oil and much cheaper than electricity. Wood pellets are renewable which cannot be said of coal, gas, oil (prime sources) and most electricity (a secondary source).
|Incineration of Waste
Waste contains a myriad of materials which generally have a stored energy derived from the sun. Instead of disposal in landfill sites which is expensive and because methane is released when it degrades, waste can be treated and burned. Incineration is one of the main ways of disposing of the waste but sometimes the energy released can be partially reclaimed by heat-driven generators or occasionally by using the product in the same way as an energy crop. Incineration is regarded by some as a good solution, mainly because it reduces the expense of landfilling. Unfortunately it creates serious environmental problems, partly due to the possible production of toxic or otherwise anti-social compounds. This contentious method is not clean but qualifies as renewable.
|Biodiesel (a biofuel)
Compression ignition internal combustion engines are common and are traditionally fuelled by diesel derived from petroleum oil. Thankfully diesel is a compound which can be replaced with biodiesel which is an organically based product and is renewable. It is relatively easily produced from plant and animal oils, fats and greases. Biodiesel also gives other benefits in the pollution stakes but the disadvantages include detriment to natural diversity and food supplies. Produced in moderation Biodiesel gets the 'thumbs up'.
|Liquefied Petroleum Gas (LPG)
An alternative to petrol (gasoline) it offers lower local pollution levels than normal fuels and vehicles that run on LPG (or are converted to) receive some subsidies in the UK. This fuel is compatible with petrol and many vehicles can run on either (bi-fuel vehicles) so the limited distribution of LPG is not a problem. Its main claims to fame are its reduced local pollution and it is also cheaper to run. Since it is petroleum based (oil or natural gas) it is not renewable and does not qualify for tackling climate change. Now if we could have a Liquid Non-petroleum Gas that would be worth shouting about.
|Liquefied Natural Gas (LNG)
and Compressed Natural Gas (CNG)
In practice, LNG and CNG are replacements for petro-diesel and suitable for heavier freight vehicles. Natural gas is intrinsically cleaner than petroleum gas but since it is a fossil fuel it is not renewable and contributes to global warming. At a local level it produces much less pollution than petrol or diesel and its use attracts financial incentives. The fuel tanks are specially designed for intense refrigeration (LNG) or high pressure (CNG) which makes them larger and heavier.
|Ethanol and Methanol (potential biofuels)
Can be used as alternatives or complements to petrol (gasoline) and can give cleaner local pollution. If the raw source is petroleum then they are not renewable but they can be produced organically (eg from sugar cane) and then they can contribute real advantages in reducing climate change. Producing these alcohols organically can also bring economic benefits, for example, to farmers. Possible drawbacks are the same as for other biofuels.
Fuel cells are not, strictly speaking, renewable or alternative energy sources, they are engines which convert energy; the energy source is actually hydrogen. We include them here because potentially they could be so important in the battle for clean and efficient energy. They are not new but the technology is complex and research and development is needed to make them more accessible. The hydrogen fuel can be derived from a variety of sources. Ideally they could be fuelled by pure hydrogen, manufactured by a renewable process, but on the other hand, they might be fuelled by some hydrocarbon compound. If the source of energy is renewable then we have a desirable situation but if it is petroleum derived, for example, then it is not a renewable system. There are developments which indicate that fuel cells may provide an important source of energy in transport applications.
|Combined Heat and Power (CHP)
This is a technique for getting more useful energy from existing generators and is not a primary energy source in its own right. Nevertheless it is included here because in providing more energy from whatever source is used (especially the dirty ones which prevail), it does contribute to reduced emissions. It is an easy option, therefore politically expedient.
Because of the global problems there is a strong drive to use alternative energy sources, if they are renewable. However, because the UK has been considered 'fortunate' in the past to have good access to fossil fuels, it has not developed the facilities to take advantage of most of these alternatives. Developing them from scratch now is expensive and that will be a negative factor for some time to come. Another major hurdle is, of course, coping with the vested interests of suppliers, distributors and politicians who support the continuation of non-renewable energies.
On the other hand, the UK is well placed geographically to take advantage of many of the renewable sources and it houses the potential technological skills.
There are plenty of winds on these islands and waves and tides around its shores, and there is a considerable amount of offshore expertise to make the most of them.
Wind power has been exploited in and around the UK to some degree but wet power which holds greater promise, but requires substantial research and development investment, has not.
What may surprise you most is that the UK receives plenty of sun as well (honest!). Nevertheless the island cannot be described as hot and sunny and so the low tech methods which only work well in hot climes are not practical and the high tech methods which could work, are expensive and need further development.
There is also agricultural potential in the UK for some of the energy crop options but other countries with less dense populations have much better prospects. This is especially true where protective, agricultural subsidies currently only contribute to over production of food and consequent waste.
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Originated: 1 December 2000, Updated:8 May, 2013