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Electricity is our fastest growing carbon

problem, aviation excepted. The means of gen-eration, distribution, storage and use all needto be addressed afresh. The governmentsefforts, through the Building Regulations, toimprove the thermal performance of new build-ings, are completely at odds with its disregardof the use of electrical energy. They haveresulted in ever-diminishing returns on invest-ment, and there are far better ways of investingin energy saving.

Causes of increases in electrical use thiscentury include gas-plasma televisions (LCD aremuch better), portable cooling units (availablefrom DIY stores), stand-by electricity and themove from analogue to digital radio, whichuses several times the energy and seems to beprogressing without anyone batting an eyelid.

For new buildings at least, this growth inelectricity use could be countered by definingcarbon zero homes as those for which on-sitegeneration would be required. Unfortunately,unlike heating, the options are very limited, themost common ones being photovoltaic panelsand wind turbines. However, the viability ofsuch devices is very sensitive to location. Arecent BRE report showed that turbines inbuilt-up areas of London or Manchester onlyproduced about a twentieth as much energy asan identical one in Wick in north-east Scotland.This should not have surprised mechanicalengineers. Wind obeys the cube-rule, wherebythe energy increases in proportion to the cubeof the increase in wind speed. If the wind speeddoubles, the power increases eight-fold.

Globally, the best renewable resource is solar

energy. North Africa receives about three timesthe solar energy of the UK. Every year eachsquare kilometre of hot deserts receive solarenergy equivalent to 1.5 million barrels of oil(about 240 million litres). Solar factories cantap into this using concentrated solar power(CSP) plants. These are quite different fromphotovoltaics, and use mirrors to concentratesunlight to create heat which is used to raisesteam to drive steam turbines and electricitygenerators. An area of just 127km x 127km cov-ered with CSP plants would produce as muchelectricity as Europe is using now.

Two German scientists, Dr Gerhard Knies andDr Franz Trieb, calculate that just 0.5% of theworlds hot deserts, if covered with CSP plants,could generate as much electricity as the worldnow uses. One square mile of desert will gener-

Under African skiesSolar factories in North Africa could soon be supplying electricity to Europe butonly to countries with more pro-active governments than the UK, says David Weight

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TREC

ate as much electricity as 100 square miles ofbiofuel crops.

Electricity could be distributed from Africaall around Europe using a high voltage directcurrent (HVDC) super-grid. HVDC only losesabout 3% power per 1000km, and the loss ofenergy between North Africa and Londonwould be less than 10%. This compares withlosses of 50% to 70% for HVAC. HVDC grids donot need to replace HVAC grids, but may bephased in, akin to upgrading road networks.

Renewable energy firm Airtricity proposeslaying HVDC cables under the sea from Africaand around Europe. This could avoid a lot of

the planning problems with associated delaysand could at least form part of the final mix.

All these systems use mirrors and a lot ofglass, but glass is made from sand and a lot ofheat. Both are plentiful in hot deserts! A spin-off is that after the steam in a CSP plant hasdone its work in driving the turbines, it is stillquite hot. Like any other thermal power plant,that waste heat needs to be removed. If seawater is used for cooling, the waste heat mayserve to create fresh water by desalination.The shaded areas under solar mirrors havemany potential uses including horticulture

using the desalinated sea water.

Countries embracing the ideaThe governments of Spain, Morocco, Algeriaand Egypt are proceeding with a number ofplants. A large CSP plant is planned south ofCairo, to supply 200,000 homes. The Germangovernment and Dutch parliament have con-firmed support for the Desertech proposal toimport electricity from solar energy in Africa.

Other supporters include President Sarkozyof France, Jonathon Porritt of the SustainableDevelopment Commission, the Climate Change

group, Friends of the Earth, Greenpeace and AlGore (see www.ted.com/talks/view/id/243 ).Meanwhile, the UK government looks set toembark on new nuclear power stations and aseries of coal power stations.

The case for a super-grid is particularly com-pelling for the UK. We could meet most of ourelectricity demands from (in order of magni-tude), wind, waves and tidal energy. Our bestresources are off the coasts of Scotland andNorthern Ireland, so need efficient transmis-sion to serve our main population centres. Thewind and waves are normally strongest in thewinter, when solar energy is at its weakest. Thisfortuitous blend could minimise any need tostore energy or fall back on fossil fuels. A

shortfall in any one area could normally be metby spare capacity in one or more other areas.For the UK, the super-grid will facilitate theexport of our renewable electricity.

The cost/kWhr is less than nuclear power(which has benefited from hidden subsidies),and, as its price equates to about $60/barrel,is now far cheaper than oil. It is still moreexpensive than gas, but a lot depends upon theprice one puts on carbon. Many commentators,including Sir Nicholas Stern, have recommend-ed that the social cost of carbon should beabout three times the figure of 25.50/t which

Gordon Brown set in December 2007. Coal maybe cheaper, but without carbon sequestrationtechnology, would be by far our dirtiest fuel interms of carbon emissions.

The complementary technologies involve

Above and far right: parabolic reflectors focus

solar rays on the heat absorber element

Map showing potential links

between various renewableenergy power stations

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different areas of expertise and it is the role ofgovernments rather than private companies tosupport them. The UK governments lack ofleadership, and reliance on a competitive ener-gy sector, militate against such an holistic andcooperative approach. This is evidenced by therecent news that Shell is withdrawing from thelarge Thames estuary windfarm scheme.Reasons cited include uncertainty about gov-ernment policy which has not enabled suffi-cient preparation and research.

As Tony Juniper of Friends of the Earth hassaid, The scale that we can do this on isabsolutely enormous if we wanted to do it.CSP plants only take two or three years tobuild, whereas nuclear takes at least 10 years.As more are built, production capacity can beramped up and costs will drop. Meanwhile, thecosts of oil and gas look bound to rise.

CSP with a super-grid offers a better securi-ty of supply, with a wider range of supplyingcountries. CSP plants are hard to disrupt andeasy to repair, and there can be strategicstores of solar energy in chemical form.

In the longer term, with potentially limitlesssolar-generated energy available, electricitycould be used for battery-powered vehiclesand railways, and the benefits can be increasedby using other energy vectors. These include

compressed air, and various gases, but themost promising is probably hydrogen, whichcan be created by using electrolysis to splitwater molecules into separate oxygen andhydrogen gases.

Hydrogen could power boilers or CHP units,or even be used for energy intensive manufac-turing processes. It is clean burning, and formswater upon combustion. Unfortunately, as anuncompressed gas, it requires excessive stor-age volume. A number of technologies look setto address the difficulties of storing and dis-

tributing hydrogen, including the use of othermaterials as carriers (see www.safehydrogen.com/default.html)

Encourage rather than enforceIf the Building Regulations are used to enforcethe use of renewable devices in poor locations,such as micro-wind turbines on houses in theshelter of tall buildings in London, there is noguarantee they will be maintained in goodorder. In many cases, the devices would neverreturn the energy invested in their manufac-ture. Instead, the sensible use of micro-gener-

ation should be encouraged through feed-intariffs rather than regulation. This involvesconsumers selling back to the grid all electrici-ty which is surplus to their own needs, at aprice higher than normal mains electricity toreflect the environmental benefit of displacingfossil fuels. This policy has been operating suc-cessfully in Germany for 10 years, and othercountries including Spain have taken up theidea. Renewables should instead be at a scaleand location where they work best. The gov-ernment must learn from its mistakes, and notexpect the private sector to take all the riskand put solutions in its lap.

David Weight is an associate at Davis Langdon

Thanks to the TREC group, especially Dr Gerry Wolff

www.desertec.org/index.html and www.trec-uk.org.uk

Left: parabolic reflectors in use in California