Today's walk ...
 |
| The group herding together against the wind |
... over Welbeck's Great Lake ...
... and past the 5th Duke of Portland's famous tunnel entrance ...
... a place visited on a previous walk (twice).
Then it was back through Creswell Crags ...
... and past one of Nottinghamshire's many solar farms.
 |
| Hunciecroft Solar Farm, Welbeck |
We have seen several of these recently on walks, including a large one during the Norfolk weekend near Cromer. There are a few in the Vale including a recently built one near Colston Basset. Out of interest I have included some details below.
Number of panels 20,000
Site area 9.7 hectares
Homes supplied 1150
Capacity factor 11%
Cost, £m £5.7 million
Feed-in tariff (FIT) 6.16 p/kWh
FIT income £303,000 per year
Export price 4.9 p/KWh
Export income £241,000 per year
Payback period 10.5 years
Life 25 years
How do we get to 5MW, the peak output of the farm at mid-day in the summer. Well, even in Nottingham the sun's power then is about 1 kW per square metre. With 20 thousand panels of 1.8 square metres and a solar to electricity conversion efficiency of 14% we get the 5MW.
But the sun does not shine all the time so the actual output is only 11% of 5MW. Comparative figures for wind are 25% (onshore) and 35% (offshore). The figure of 11% may seem very low, but it's worth pointing out that these solar panels are ten times better at capturing the sun's energy than any crop grown in this country. Photosynthesis is hopelessly inefficient when used for this purpose.
The sizes of these schemes are often quoted in terms of how many homes are supplied. This is calculated by dividing the average farm output in kW by the average domestic electricity use of about ½kW - hence 1150 homes.
I have calculated a payback period (actually this is simply the cost divided by the annual income based on the current so-called feed-in tariff (a subsidy to encourage investment in renewable energy of 6.16p/kWhr) and an assumed export price of electricity of about 4.9 p/kWh and you can see that this is 10.5 years. Not bad, but this is actually an oversimplification and does not take account of financing costs, inflation, maintenance and panel degradation of ½% a year. In fact investors have been promised an annual return of 7%. In addition, the farmer can graze the field so the loss of land for agriculture is not as high as might be assumed.
HOWEVER, this feed-in tariff has just been reduced to about 1p/kWh. The government admits that the proposed reductions would wipe 6GW off UK renewable generation capacity by 2020/21. And this just ahead of the climate change conference in Paris! Well, what do you expect from the new Energy Secretary whose first pronouncement was "Britain’s new nuclear power stations ... must be designed to look beautiful to garner essential public support".
Well, glad to know everything is under control then - but just in case, get your candles out!
