Solar Energy

1. Solar Energy Approximately 1000 - 10000 times as much energy falls on the Earth as is currently used for all purposes. Government Energy Review suggests that 50% of UK electricity demand could be met from solar energy by 2050 - but at a cost

2. Renewable Energy Non-Solar Solar • Direct • Passive • Active • Indirect • Hydro • Wind • Wave • Ocean Thermal Currents • Biomass/Waste • Salinity gradients • Geothermal • Tidal

3. Direct Solar Energy • Passive • Building Design • Active • Hot Water Systems • Photo Voltaic • Centralised Solar Thermal Stations • Satellite Solar Stations • Solar Ponds Applicable in UK yes yes yes no no no

4. Passive Solar Energy • Optimises available solar energy capture by appropriate building design. • Larger South facing Windows • Need to reduce heat loss - insulation (roof, walls, double glazing) • But double glazing also reduces potential solar gain • Reducing size of north facing windows may be counter productive as more lighting in those rooms may be needed (and/or may appear dark). • Design must consider all effects

5. Solar Gain for windows of different orientation. 51o N Note: Maximum Solar Gain for south facing windows DOES NOT occur in June

6. June Mar / Sep Dec South Window The south facing window paradox In June most solar radiation is reflected

7. June Even with reduced solar gain in June, overheating may occur Provide overhangs to shade the window from direct sunshine from May - August South Window

8. Advanced Passive Solar Energy Design Control of vents and shades essential to avoid overheating and optimum savings

9. Passive Solar Energy Conservatories • Are they beneficial? • Can trap heat in winter • Provide additional insulation for glazing • Can reduce energy demand • But • Can lead to over-heating in summer • Can be very energy wasteful if conservatory is used as an additional heated living space in winter.

10. Solar Energy • Passive • Building Design • Active • Centralised Solar Thermal Stations • Satellite Solar Stations • Solar Ponds • Hot Water Systems • Photo Voltaic Applicable in UK yes no no no yes yes

11. Centralised Solar Thermal Stations Centralised schemes - Bairstow California Experimental plant 100 - 1000 MW have been built, but most have proved to be unreliable

12. Each heliostat mirror must be independently tracked

13. Part of central reflector

14. Large satellite solar array Microwave transmitter Microwave receiving aerial on earth Sattelite in Geo-stationary Orbit Microwave Beam Solar Satellites

15. 2m Strong Salt Solution Solar Ponds Fresh water acts as insulator Salt water and base of pond act as the absorber Fresh Water

16. A Solar Pond Technology is being researched in Israel and USA

17. Solar Energy • Passive • Building Design • Active • Centralised Solar Thermal Stations • Satellite Solar Stations • Solar Ponds • Hot Water Systems • Photo Voltaic Applicable in UK yes no no no yes yes

18. A simple Hot Water System Supplementary electric heating is possible, but not desirable from an Energy or Environmental standpoint. Problems: 1) Reliance solely on solar water heating 2) Temperatures of storage will be low and at temperatures likely to breed Legionnaires bacteria

19. A Solar Hot Water System with 2cylinders Normal Hot Water system cuts in only when solar supply is insufficient for demand. Savings of 50 - 60+% are possible - depends on demand and collector area

20. Washing clothes Washing dishes Washing dishes 3 minute shower Washing dishes Solar Hot Water supply and demand bath bath Solar Contribution 48% - using 2 sq m

21. Solar contribution 48% with 2 sq m 72% with 3 sq m 96% with 4 sq m ? 5+ sq m??????? Clear Sunny conditions Solar contribution 33% with 2 sq m

22. Solar Hot Water supply and demand Most periods of demand require significant input from boiler. Solar contirbution with 2 sq m collector - 17%

23. Typical cost is £1950 for a 3 sqm panel and fittings (excluding VAT and fitting). Total ~ £2900. • Over the year these might provide 50-60% of hot water. • A typical household uses 165 litres of hot water a day requiring around 3150 kWhr of energy. How cost effective is solar hot water? • Heat by gas condensing boiler: --------------- £46 • Heat by older gas boiler: ……………... £59 • Heat by electricity …………………….. £189 Pay back is in 127 years (gas condensing), 100 years (gas), 31 years (electricity)

24. Can solar hot water heating be cost effective on existing properties? • Mass production could reduce costs to around 50 - 60%, but installation costs wil not change. • Total cost ~ £2000 • pay back in 70 -90 years with gas - or 20 years with electricity If Government provided a subsidy of say £1000 per unit then pay back would still be around 40 years - comparable to double glazing. An expenditure of £0.5 billion per year for 20 years could provide the necessary subsidy to ensure all potentially suitable houses have collectors. Would save 5 - 10% of energy use in home

25. Other factors which would make Solar Hot Water heating more attractive. Energy prices rising - but that is contrary to trend in last 20 years Require all new houses to have solar collectors - installation costs much reduced - probably would make houses £1400 more expensive

26. Solar Energy • Passive • Building Design • Active • Centralised Solar Thermal Stations • Satellite Solar Stations • Solar Ponds • Hot Water Systems • Photo Voltaic Applicable in UK yes no no no yes yes

27. Solar Photo Voltaic • Direct production of electricity from sunshine • Costs fell dramatically between 1970 and 1990, but have seen less movement in last decade. • Prices are between 5 and 8 times cost of gas generation • 10 - 16p per kWh compared to ~2p per kWh Domestic Consumers pay around 6 p per kWh • Problem: • Photovoltaic cells provide electricity in Direct Current form • Almost all appliances run on Alternating Current Needs inversion to AC and ideally also batteries for storage

28. Solar Photo Voltaic • Installation costs for a typical house range from £7000 - £20000 depending on size of array. • Mass production and mass installation in a local area could reduce cost by 30%. • An 40 sq m array costing around £20000 would be needed to provide the equivalent of annual demand. How is demand going to be met? Problem of storage Batteries?

29. Solar Photo Voltaic • Photovoltaics are ideal in remote locations where electricity supply does not currently exist • e.g. Third World Countries remote from electricification • > refrigeration for vaccines • In UK applications such as • remote telephone boxes • power for road signs (in conjunction with wind) - A140 south of Norwich)

30. Why not sell and buy from the Electricity Supply Companies Prices paid by Suppliers vary dramatically over the day

31. Solar Energy Concluding Remarks Solar Energy has a large potential even in the UK Ideal in locations where electricity is not currently installed • BUT active solar energy • is expensive and not cost effective • Energy Prices are too cheap • Solution: • Government Grants ~ £1000 per unit • or Tax Credit? • Upgrade Building Regulations to require solar hot water heaters Potential savings in CO2 very approximately 30 - 60 Mtonnes