Can renewables meet the need?

A recent tweet celebrated the supposed fact that at peak, recently, Germany derived 25% of its power from solar. The source given was data published by the Fraunhofer ISE at https://www.energy-charts.de/power_de.htm.  But is the claim true?

Actually no. The highest proportion in recent weeks was reached during August 2nd when a combination of low demand, low winds and strong sun produced about 56% of Germany's electric power from solar pv. A very good result - though obviously excluding fuels used for space heating, travel, etc.

But it's a power number - a measurement over a short time - specifically the middle of the day. There is no solar power at night and not much in the early morning and evening. A bit of rough analysis for a more representative day, 27 July in fact, shows that solar produced 22% of the power at peak but 10% of the day's energy. Extra investment in solar PV could increase the peak as much as you like - even to 100% - but that would still need over 50% of the energy to come from somewhere else (possibly wind or a storage system).

And this is mid summer.

A similar analysis for January shows a solar PV power peak of c8% but providing only c2% of the day's electricity. And the average over that week is much worse.

Is wind the answer? Sort of. Germany gets more energy from wind than from solar PV and it's available at night and in winter. But it's even less predictable than solar. At midnight on January 5th it provided just 3% of the needed electrical power.

Moreover periods of low wind can last for days - there was almost no wind for the whole seven days starting January 17th.

There are partial low-carbon solutions - nuclear, tidal, hydro, import of power from very large new solar farms in north Africa and various kinds of storage - but they all have their own problems.
Any responsible plan for our energy future must show how it would cope with periods like 17 to 14 January - and at what cost.

Wind farms perform better than we feared

Some commentators have claimed that the performance of wind farms will decline catastrophically with age. For instance, a report by Prof Gordon Hughes for the Renewable Energy Foundation claimed that the “normalised load factor for UK onshore wind farms declines from a peak of about 24% at age 1 to 15% at age 10 and 11% at age 15”. That implies an annual worsening of about 5% and would presumably be due to mechanical wear. 

It would greatly reduce the long-term value of wind farms both economically and as sources of low-carbon electricity.

Fortunately a more recent study, Staffel and Green, 20 13, suggests that it isn’t true. This is an extremely detailed study which draws on very large quantities of data about both weather and wind farms. The authors show that, though wind farm performance varies considerably:

•  The initial load factor is 28.5% not 25%.
•  The annual performance loss is about 1.6% not 5%.

This is good news for investors in wind farms and for the climate.

References

Hughes, Gordon, 2011: The Performance of Wind Farms in the United Kingdom and Denmark. 2012, London: Renewable Energy Foundation. URL: http://tinyurl.com/cn5qnqg.

Staffell, Iain, and Green, Richard, 2013: How does wind farm performance decline with age? Renewable Energy. Volume 66, June 2014, Pages 775–786. URL: DOI: 10.1016/j.renene.2013.10.041.

Renewable Energy and Enfield

[This post was originally written for the newsletter of the Enfield Society - which will print part of it.]

In planning applications and fuel bills, on Welsh hillsides and in the North Sea, we keep hearing about renewable energy. But why? What’s the fuss about?

Let’s start at the beginning. Our economy is based on fossil fuels. Gas and oil heat our houses. Petrol and diesel fuel our cars. Coal and gas generate most of our electricity.

It has to stop. The overwhelming majority of competent scientists agree that burning fossil fuels has already increased global temperatures, raised sea levels, melted much of the Arctic ice and made extreme weather events more likely. If this continues island and coastal communities will lose their homes, arid regions will dry out and global food production will fall.

And we have to move fast. To avoid catastrophic climate change we need to reduce global greenhouse gas emissions by 3% pa, starting now. The later we leave it the faster we’ll have to cut emissions. Also, since the UK’s prosperity is derived from our coal-fueled industrial revolution which has so polluted the atmosphere it’s only fair that we should cut our emissions sooner and faster than countries, like India and China, that are still industrialising.

Our first thought should obviously be to use less energy (and thus save money!). We can do this by improving building insulation, buying more efficient equipment, replacing things less frequently and driving and flying less. 

There a LOT of scope for this. Homes built to the highest standards (passivhaus) need 90% less heating energy than average homes. Unfortunately Enfield Council has refused to mandate this level of performance despite repeated representations from Enfield Green Party. There's also scope to provide the heating that is needed, especially in existing buildings, by using ground and air-source heat pumps rather than conventional boilers.

In addition the most energy efficient cars, computers and domestic appliance are much more efficient than average ones.

That will not be enough. We must also stop burning fossil fuels and move to low-carbon energy sources. Our existing nuclear power plants must play their part but new nuclear plants simply cannot be built fast enough or cheaply enough or run reliably enough to meet the need even if the waste disposal problem was solved – which it isn’t. Renewables will have to carry most of the load.

Fortunately there are lots of renewable energy sources: hydropower, sunlight, wind, waves, tides, hot underground rocks, spare heat from furnaces and sustainably produced fuels. Each of these has its pros and cons. How can Enfield play its part in the renewables revolution? How, in short, can we cut our greenhouse gas emissions and create the green jobs our people need?

We can exclude waves and tides (no sea) and hot rocks (wrong geology). Large hydroelectric schemes are also out though I believe that the Council plans a small turbine in the River Lee.  The Council also plans a heat network to distribute spare heat from the Edmonton incinerator.  That’s low-carbon energy provided that it’s our last resort for dealing with waste. Reuse and recycling are clearly better options where available. It may also be possible to add other sources of spare heat to the heat network or to support another heat network.

Could we use sustainably produced fuels in a heat network or even in cars? Perhaps. In the UK today these fuels are mainly biodiesel from vegetable oil and some sustainably produced wood. In practice the biodiesel isn’t always low carbon due to the deforestation that precedes palm oil production. Further, the UK already has a number of power stations that burn woodchips and other biofuels with others planned but their appetite for fuel greatly exceeds the supply of sustainably-produced fuel – even allowing for imports. The greenwash is particularly thick in this sector!

With appropriate regulation this may become an important sector as there are several novel fuels under development. However, these are all possibilities for the future not fuels we can use now.

So we come to the big ones: sun and wind.

Wind is actually a bit marginal in urban areas. Big turbines are impractical, small turbines are inefficient and may damage any wall or roof they’re attached to. Larger turbines might be installed in the north of the borough – though the many restrictions would make it hard, perhaps impossible, to find suitable sites.  To me wind turbines are elegant and stately. I like them. Some people object to them on aesthetic grounds but there’s no accounting for taste is there?

Finally sunlight. We could all use sunlight to heat our water and generate electricity. Government subsidies (Feed-in Tariff and Renewable Heat Obligations to be technical) make investment profitable for the homeowner whilst contributing power to the grid. Unfortunately Enfield lags behind on solar electricity – only one home in 362 has solar panels – compared to 1 in 8 in Waltham Forest. Enfield has only 1.5MW of installed solar capacity.

Solar PV is not limited to private homes. The Council has installed panels on the Civic Centre and on schools. Many offices and factories could also benefit from solar panels. As a Green I’d like to see the Council make this mandatory for new and existing buildings. But national legislation make this impossible and the need to persuade hundreds of employers and to co-ordinate thousands of installations in a voluntary programme is daunting. And speed is vital.

That’s why I support the proposed solar array for Sloeman’s Farm. Once approved it would provide 15MW within just a few months. That’s ten times Enfield’s current solar capacity and it would increase London’s solar capacity by 30%. No other current scheme can do so much so fast.

Renewable energy is not a fad. To reduce our greenhouse gas emissions, fast, is an obligation we owe to future generations, to people in low-lying lands and to all the species threatened by climate change. Inaction is not an option I can live with.