MacKay doesn’t neglect offshore wind either, but is distressed by its cost and the relatively limited amount of sea which would really be suitable for it. But again, he’s more than ready to factor in vast amounts of offshore wind into future plans — just to see if it really can keep the lights on.
MacKay also gets into solar, both the thermal and electric kinds. Thermal has some potential for home energy, it seems, and is a good idea. (Funnily enough, almost all home microgeneration kit in the UK right now is solar-thermal water heating, so he might just be right here.) But solar photovoltaic (PV) electricity is viciously expensive in the cloudy UK, and just sticking panels on roofs won’t do much — it seldom yields any large proportion of the energy used in the building it’s on top of. You need to cover a big portion of the country in cells.
All in all, according to MacKay, if you like solar it probably makes more sense to put the panels in North Africa and bring the power to the UK over efficient high-voltage DC lines.
As an engineering matter the desert-solar idea is quite feasible — not very different in scale from piping in gas across continents and beneath seas, as people already do. Those fretful about buying power from Russia or the more unsavoury Gulf oil producers might be equally unhappy to buy it from Libya or Algeria, however.
Then, of course, there’s biofuel. MacKay ignores the matter of food prices to begin with, but still finds that biofuel crops demand vast amounts of land to produce quite limited energy yield. he notes that once upon a time the human race generated nearly all its energy from biomass fuel, but that only worked with a Middle Ages living-standard and population.
The most efficient plants … deliver an average power of 0.5W/m2. Let’s cover 75 per cent of the country with quality green stuff. That’s 3000m2 per person devoted to bio-energy. This is the same as the British land area currently devoted to agriculture. So the maximum energy available, ignoring all the additional costs of growing, harvesting, and processing the greenery, is … 36 kWh/d per person.
Wow. That’s not very much, considering the outrageously generous assumptions we just made, to try to get a big number.
MacKay also considers tidal power and hydropower, and assumes that they will be used to the fullest. Being interested in using erratic wind power on a big scale he sees that massive wind needs massive backup. He makes estimates on the two most eco-friendly backup systems: battery storage in millions of electric vehicles plugged into the grid, and pumping huge quantities of water uphill, so as to release it via hydropower turbines when needed during windless days or demand spikes.
He also floats another nice idea, intelligent appliances which can sense the grid’s pain during times of high demand and ease off on their power demand automatically. However, having assumed these are widespread, he still sees a huge need for pumped-water storage in any wind-heavy future grid.
Fridges can be modified to nudge their internal thermostats up and down just a little in response to the mains frequency, in such a way that, without ever jeopardising the temperature of your butter, they tend to take power at times that help the grid.
Popular soap operas such as Coronation Street and EastEnders typically generate TV pick-ups of 600–800MW … automatically switching off every fridge would nearly cover these daily blips of concerted kettle boiling.
Fluctuations in wind power will be a different matter.