1. Prospects for Solar Energy in the UK 2010-2030 Kathryn Greatorex 24th February 2005
I have been studying the possible contributions of solar energy in the UK by looking at 2 very different systems- solar thermal systems and photovoltaics.

2. Solar Energy Systems Considering 2 types of system:
Solar Thermal systems for domestic water heating (DWH)
Solar thermal systems are basically systems to heat water mainly for domestic consumption. These systems offset the demand for gas and electricity by reducing the requirements from conventional boilers and emersion heaters.

3. Images from http://www.solarcentury.co.uk (2005)
Photovoltaic cells generating electricity
Images from (2005)
Excluding passive solar energy
Photovoltaic cells directly produce electricity and will therefore supplement energy taken from the National Grid, reducing the demand for electricity derived from fossil fuel powered stations.
I have excluded contributions from passive solar energy in these analyses because not only would it be very difficult to try and quantify, but also without substantial alterations to the design of future houses and alterations to the current housing stock which is extremely impractical, passive solar energy is not expected to contribute significantly more energy in the period we are looking at.

4. Household Assumptions
24 million current households in the UK
10 million suitable for solar installations
~180, 000 new homes built each year
50% suitable for solar installations
To project the contributions that solar energy systems could have by 2030 I studied the 2 systems separately. I looked individually at outputs that could be made from both new houses and the current house stock, and then totalled these up to give an overall projection for each 5 year period.
I have assumed that about 10 million of the current housing stock would be suitable to install either of the solar energy systems, and that half of the approximately new homes built each year will also be suitable.

5. Installation Rate Assumptions - Thermal & PV -
New Homes- 90, 000 per year
Retrofitting- assuming increased installation rates over the period as the industry builds up.
Installation rate (per year)
90, 000
110, 000
160, 000
250, 000
400, 000
The overall, cumulative projections that I make for solar energy contributions are presuming that installations start in 2005.
For new houses this means that homes will be installed with solar thermal and PV technologies by the end of the year. This installation rate is kept constant throughout the period.
Where retrofitted systems are concerned what I have done is to estimate realistic installation rates (as shown on the table) which includes both systems and then project the additional outputs that these systems could make.
I initially assumed that installation rates would be the same as for new homes, but then increase throughout the period to take into account a presumed build up the industry of manufacturers and installers alike.

6. Solar Thermal Assumptions
3 sq m of thermal panels per rooftop
350kWh/m2/year output
Therefore 1050 kWh/year per house
Constant output assumed
- Current Energy Payback Time: ~2.8 years
For solar thermal systems I have assumed that each suitable house has 3 sq meters of thermal panels and the output for each squ m is 350 kWh per year. This gives a total output of 1050 kWh per year for each house.
The output figure was derived from data collected by Keith for the installation on his house. It gives a more realistic potential output than the 500 kWh output stated by the manufacturer.
I have not increased the possible outputs from these systems over the projection period, as I have done for PV systems as you will see later on, because there does not seem to have been much recent technological progression in this field that could significantly enhance system performances.
By multiplying the output by the number of installations possible I project that in each 5 year interval an additional 1.7PJ of energy could be provided by solar thermal systems on new houses leading to 8.5PJoules in total by In that time a further 19PJ could also be provided by retrofitted systems.

7. Photovoltaic Assumptions
New Homes: 15 sq m
Retrofitted systems: 12 sq m
Output increases over the next 25 years
Current Energy Payback Time: ~14 years
Output (kWh/m2/yr)
100
120
150
180
200
I used the same kind of procedure to estimate the possible contributions PV cells could provide, but there are subtle differences.
I am assuming that new homes install 15sq m of PV cells whereas retrofitted homes install 12sq m because of having to work with the existing roof structure rather than being able to integrate the system into the design at the construction stage.
These areas will obviously vary depending on roof areas available, but I took these figures to be the average areas that could be occupied by the new style of PV cells like sun slates that are compact and designed to fit onto UK roofs to try and maximize the area available.
I have also assumed that the potential outputs from PV arrays will double over the next 25years to 200 kWh/m2/year as shown by the table on the slide. That is because I believe research and development will continue and technological advances will progress in the component parts and manufacturing procedures.
I’ve assumed the same installation rates for PV as for solar thermal systems.
Using these assumptions I project that by 2030 new homes could provide about 13½ PJ and retrofitted homes 37 PJ.

8. Energy Projections Energy Supply (PJ) By… Solar Thermal PV Total (PJ)
2010
3.4
4.3
7.7
2015
7.2
10.1
17.3
2020
11.9
19.0
30.9
2025
18.3
33.1
51.4
2030
27.6
55.2
82.8
I grouped together the totals for each type of house for both systems to give system based projections and then added them together to give an overall estimate for the total solar contribution that could be made to energy supply in the UK.
These figures show a steadily accelerating energy contributions that could be made from solar over the period.

9. Energy Projections
This is easier to observe on this graph. The Pink line shows projections for solar thermal energy, the green line for PV with the blue line showing the total overall potential. This looks a very promising energy resource for the future.
Initially costs and energy inputs will be high, but the potential to offset gas and fossil fuelled electricity could be significant as long as systems are widely implemented.
I project that by 2030 it could be possible for solar energy to provide 83PJ.

10. In my investigation I also went on to estimate energy and cost payback times over the period for the systems to show their viability and indicate the level of subsidy support that the government would have to supply to provide incentives to implement the systems so that contribute to the energy supply.
Energy payback times were a lot more favourable for both systems that the cost payback times
Having researched the energy inputs into the manufacture of these systems the energy payback times seem relatively reasonable in comparison to their lifetimes which are about 20-30years. Solar thermal systems payback their energy in about 2.8years, PV systems are not so good at about 14 years currently.
However, cost paybacks are a lot less favourable for both systems, but especially PV- meaning that subsidisation is currently essential – as is likely to be throughout the period