Other renewable technologies: debunking the myths

Potential problems with personal-scale renewable energy

Each renewable energy technology has different advantages and disadvantages, and each is more suited to some applications than others. Generally speaking renewable energy sources are ‘clean' (i.e. low in carbon emissions) and indefinitely sustainable; whereas conventional fuels are ‘dirty' (i.e. high in carbon and climate-change related pollutants) and represent a finite resource. However, just because a renewable energy resource is clean (such as wind or water power), it does not follow that the technologies used to harness that resource (such as wind turbines or hydro power systems) are always beneficial. It would be a mistake to assume that all renewable technologies are environmentally friendly in all situations.

A crucial factor is the potential benefit offered by a renewable energy technology compared to the impact or damage caused by its manufacture and installation. A large industrial wind farm, for example, can generate as much energy in its first six or eight months of operation as was required initially to manufacture the turbines and construct the site. A typical wind farm will have a service life of 15 years or more, so this represents at least 14 years of worthwhile renewable energy production. On the other hand, a very small wind turbine sited in a private individual's garden is likely to produce so little useful electricity that it will often not replace the energy used in its construction. Thus, although micro-scale wind power is a renewable technology, in most situations it is clearly not a worthwhile one if it causes more environmental damage than good.

The same can be true of domestic-scale photovoltaic installations, micro-CHP, small-scale hydro power and domestic-scale rainwater harvesting systems. All too often, supposedly eco-friendly technologies simply do not make environmental sense when implemented on a personal level.

The advantage of personal-scale heating and hot water systems

Heating and hot water are a different matter altogether. Almost every house already has its own heating system and its own hot water system. Here is an opportunity, therefore, to implement renewable technologies which will make a real environmental difference on a personal level. This is why Organic Energy has taken the decision to concentrate specifically on offering sustainable domestic-scale heating technologies.

Many renewable energy systems generate electricity, but we must remember that electricity only represents one quarter of our total energy usage in the UK. Even if we can meet the government's target of generating 20% of our electricity from renewable resources, in fact this represents only 1/20th of the UK's total energy consumption. Other energy consumers such as heating and transportation are equally important in terms of reducing carbon emissions. Renewable electricity is important but is only a small part of the solution; as individuals if we could produce all of our heating from renewable resources this would immediately cut another 25% or more of our personal carbon emissions. This is another reason why we have decided at Organic Energy to offer genuinely renewable solutions to the problem of providing heating and hot water.

There follows a comparison of other renewable heating and hot water technologies with the biomass and solar thermal systems we offer at Organic Energy.

Ground Source Heat Pumps (GSHP) in comparison with biomass central heating systems

A ground source heat pump works by removing some of the heat from an area of ground such as your garden or lawn through a buried network of pipes, and using this energy to provide central heating. In principle a GSHP system is very similar to a fridge working in reverse: a pump is used to remove heat from one place and move it to another.

A GSHP system typically removes only 1^oC or 2^oC from the ground, so the pump unit has to work hard in order to make the water hot enough for your radiators. The pump unit itself uses electricity in the same way that a fridge does: for every 3kW of heat released from the ground, about 1kW of electricity is used by a GSHP unit. This sounds like excellent efficiency... but what many GSHP manufacturers do not tell you is that this advantage is completely negated by the fact that electricity itself is inherently a very inefficient form of energy.

A coal or gas fired power station is typically only 40% efficient because most of the energy is wasted as heat rather than converted to electricity. This already represents a large inefficiency. And when we add the transmission losses of the national grid to the equation we see that electricity is less than 35% efficient: for every 3kW of coal or gas used at the power station, only 1kW of electricity reaches your home. This completely reverses the apparent efficiency advantage of a GSHP. In fact you might as well just heat your house with a conventional ‘dirty' fossil fuel such as oil, coal or gas.

An alternative source of electricity which could be used to drive a GSHP is of course nuclear power. But can a GSHP system really be considered an environmental option if it relies on the construction of a new generation of nuclear power plants in the UK?

Some claim that if a GSHP is powered by renewable electricity this represents a genuinely renewable heating system. But this also is largely untrue. Renewable electricity is already in short supply, and is far too precious a resource to waste on such power-hungry purposes as heating: imagine how many wind farms would be required if every house in the UK used a GSHP! Even if a GSHP is powered by a private renewable energy source such as an array of PV solar panels, it still does not make environmental sense: the amount of energy and silicon that went into manufacturing those solar panels is likely to far outweigh any energy saved during the operation of the GSHP system. And solar electric panels produce most of their energy at the height of summer - precisely when central heating is not required!

The fundamental problem is that a GSHP does not utilise a primary energy source but instead relies on electricity. Unlike biomass heating which directly uses wood as a primary source of sustainable energy, a GSHP cannot be considered a genuinely renewable energy system.

Please see the wood pellet heating systems page to learn more about the advantages of using wood as a clean source of renewable energy.

Solar Electric/Solar Photovoltaic (PV) in comparison with solar water heating systems

Solar electric systems, also known as solar photovoltaic or solar PV, generate electricity from the sun's energy, whereas solar water heating or solar thermal systems use the sun to warm up water for baths and showers, washing machines and other domestic purposes. Although they are both loosely termed 'solar energy', they in fact very different technologies.

Solar photovoltaics remain a very expensive form of renewable energy. Although the manufacturing cost has been steadily decreasing in recent years, even today a domestic scale PV installation will normally take several decades to ‘pay back' the cost of its installation in both monetary and energy terms.

Solar water heating, on the other hand, is often the single most cost-effective renewable energy technology available for domestic and small business applications. A typical solar water heating installation from Organic Energy could provide over 50% of your domestic hot water, and if you currently use an expensive form of water heating such as an electric immersion heater or an LPG boiler for example, then the cost of installing a Gasokol solar water heating system could be recovered in as little as ten years in savings on your fuel bills. In comparison, how many banks would provide such a favourable rate of return on your savings?