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

Renewable Energy

Non-Solar

Direct

•Passive•Active

Indirect•Hydro•Wind•Wave•Ocean Thermal Currents•Biomass/Waste•Salinity gradients

• Geothermal

• Tidal

Solar

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

Direct 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

Passive Solar Energy

Solar Gain for windows of different orientation.

51o N

Note: Maximum Solar Gain for south facing windows DOES NOT occur in June

In June most solar radiation is

reflected

June

Mar / Sep

Dec Window

The south facing window paradox

South

June

WindowSouth

Even with reduced solar gain in June, overheating

may occur

Provide overhangs to shade the window

from direct sunshine from May - August

Advanced Passive Solar Energy Design

Control of vents and shades essential to avoid overheating and optimum savings

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.

Passive Solar Energy

Conservatories

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

Centralised Solar Thermal Stations

Centralised schemes - Bairstow California

Experimental plant 100 - 1000 MW have been built, but most have proved to be unreliable

Each heliostat mirror must be independently tracked

Part of central reflector

Large satellite solar array

Microwave receiving aerial on earth

Microwave transmitter

Microwave Beam

Sattelite in Geo-stationary

Orbit

Solar Satellites

Solar Ponds

Fresh Water

Strong Salt Solution

2m

Fresh water acts as insulator

Salt water and base of pond act

as the absorber

A Solar Pond

Technology is being researched in Israel and USA

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

A simple Hot Water System

Problems:

1) Reliance solely on solar water heating

2) Temperatures of storage will be low and at temperatures likely to breed Legionnaires bacteria

Supplementary electric heating is possible, but not desirable from an Energy or Environmental standpoint.

A Solar Hot Water System with 2 cylinders

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

South facing Collector (June)

0

1

2

3

4

50 2 4 6 8 10

12

14

16

18

20

22

24

Time (hrs)

En

erg

y (

kW

h)

store

boiler

demand

solar gain

bath

bath

3 minute shower

Washing dishes

Washing dishes

Washing dishes

Washing clothes

Solar Hot Water supply and demand

Solar Contribution 48% - using 2 sq m

South facing Collector (June)

0

1

2

3

4

50 2 4 6 8 10 12 14 16 18 20 22 24

Time (hrs)

En

erg

y (k

Wh

)

store

boiler

demand

solar gain

East facing Solar Collectors (June)

0

1

2

3

4

5

0 2 4 6 8 10 12 14 16 18 20 22 24

Time (hrs)

En

erg

y (k

Wh

)

store

boiler

demand

solar gain

Solar contribution

48% with 2 sq m

72% with 3 sq m

96% with 4 sq m

? 5+ sq m???????

Solar contribution

33% with 2 sq m

Clear Sunny conditions

South facing collector (December)

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time (hrs)

En

erg

y (k

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store

boiler

demand

solar gain

Solar Hot Water supply and demand

Most periods of demand require significant input from boiler.

Solar contirbution with 2 sq m collector - 17%

•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.

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)

How cost effective is solar hot water?

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

Other factors which would make Solar Hot Water heating more attractive.

Energy prices rising -

but that is contrary to trend in last 20 years

1980 1990 2000Coal 100 91.7 87.1Electricity 100 96.2 75.3Gas 100 115.7 89.6Petrol 100 93.2 108.8

Require all new houses to have solar collectors - installation costs much reduced - probably would make houses £1400 more expensive

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

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 kWhProblem:

•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

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.

Problem of storage

Batteries?

How is demand going to be met?

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)

Why not sell and buy from the Electricity Supply Companies

Prices paid by Suppliers vary dramatically over the day

UK Electricity Demand

0

10000

20000

30000

40000

50000

60000

00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00

Time (hrs)

MW

17-18th December 2001

29-30th April 2002

6-7th May 2002

Solar Energy Concluding RemarksSolar 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