Eco-centre has its finger on the pulse of zero-carbon electricity

EXTINCTION Rebellion, the declaration of climate emergencies by the UK and Welsh governments and the announcement of a Green Deal by the EU Commission President does require a response from those, including myself, interested in the future energy supply in the UK and for me in particular, Wales.

Last November the Centre for Alternative Technology (CAT) in Machynlleth released its latest version of the Zero Carbon Britain (ZCB document.

It is a superb quantitative piece of work which enables a detailed discussion of the possibility that a zerocarbon Britain could be achieved by renewable sources alone.

With the exception of the Renewable Energy Future report from the Swansea Bay City Region no other report from Wales is remotely at the standard of the CAT’s.

A good starting point for a quantitative discussion is to quote the present wholesale and retail prices of electrical energy in terms of the kilowatt hour (kWh) — namely 5p per kWh and 16p. One kWh would be the energy expended by a 2kW-power kettle boiling for half an hour.

Note also that the cost 16p per KWh is exactly the same as the cost expressed as £160 per megawatt hour where a MWh is a thousand kWh.

And it’s good to have an idea of the investment required to reduce the UK energy demand.

If we were to insulate and supply ground or heat pumps for the 35 million domiciles in the UK at, say, £7,000 each, the bill would be £245bn; the UK annual GDP is £2,100bn

This is an area where Wales has considerable expertise and an industry could start up anywhere, including deprived regions, particularly as the Welsh Government has just embarked on a £400m house-building project.

Tree planting has already started and will no doubt be expanded, with each tree absorbing 2 kilograms (kg) of CO2 per year.

The CAT ZCB document foresees the electricity demand rising from the average power demand of 30 gigawatt (GW and which is a million kilowatts or a billion watts) in 2017 to 56 GW in 2050 where domestic heating and transport are largely electrified.

Over the same period the average power generated increases from 33 GW to 90 GW, well in excess of the foreseen demand in order to supply electricity storage.

Note that these are average powers — at 6pm on a cold day in winter the 56 GW average power demand can rise to 80 GW, and fall on a day in early summer to 30 GW.

In the ZCB scenario electricity generation from the wind increases from an average power of 5GW today to 69 GW in 2050, a 14-fold increase (3 times onshore and 15 times offshore wind generation).

It is foreseen that electricity from onshore, offshore and floating offshore wind will cost 4p per kWh by 2022.

Electricity from solar generation is planned to increase from 2 GW today to 9 GW in 2050 at a cost just under 4p a kWh.

There is no nuclear contribution (7 GW today) and there is no reliance on imported electricity, although excess electricity is exported.

Miscellaneous generating sources, such as oil and coal, decrease from 5 GW today to 3 GW in 2050.

Electricity generation from natural gas decreases from 14 GW today to 1 GW from natural gas obtained by a green method, which forms the basis for electricity storage.

In the CAT ZCB scenario there is a 3 GW contribution from wave and 5 GW from tidal power, some 9% of the total generation.

Since little is the success of wave power to date despite 40 years of trying and tidal range/stream generation is certainly predictable but predictably complex and problematic, these contributions are certainly not guaranteed.

From Mark Shorrock’s request for investment of £1.5m to keep his Swansea Bay Lagoon proposal alive, to the Hendry report and indeed the Severn Barrage proposal, the serious implications of the lunar day perodicity (four periods of three hours’ generation within 24 hours and 50 mins) and the spring/neap tide leading to an output power variation of a factor of three have not been at all made clear

The 2.7 GW average power of a Severn Barrage, with all its variability, would not be a large contributor to the demand of 57 GW foreseen in the ZCB.

An array of lagoons would have produced a similar average power output with the daily variability somewhat ameliorated, but still present, as is the spring/ neap tide variability. Provided customers can be found willing to pay for the Swansea Bay Lagoon electricity then the project might well go ahead and investors/pension funds would be making reasonably secure investments. However, governments have to make sure that public funds are directed at projects with the best prospects of achieving carbon neutrality in the face of the climate emergency. Electricity from tidal and marine generation is expensive, in the range 15 to 30 per kWh.

Lagoons can provide a defence against rising sea levels, but at the expense of electric power generation

As noted, the average generated power in NAT ZCB is some 4GW above the demand so that the surplus generation can be used to produce though electrolysis, hydrogen which can be used for rail transport and heavy goods vehicles and to produce “green” natural gas for storage.

This process is exemplified by Exytron’s three-stage process to “greenpower” a block of 70 flats in Rostock, Germany. The first stage is based on green electricity from a 30 kW solar PV array on the roof which electrolyses water into hydrogen and oxygen.

In the second stage hydrogen is combined with CO2 (from the third stage of the process) to form (natural gas) which is combusted with the oxygen from the first stage, to produce electricity, CO2 (used in the second stage) and water.

Based on 34 years of weather data the Met Office reports that approximately 10 times a year the wind capacity factor drops below 25% for four days in a row, and once in 10 years it falls below 10% for 8 days in a row.