od energy group read

March 30th 2009. Join the Group Read. Chapter 18. A first balance (Instructions on how to join are at the bottom of the original post) This is the first chapter attempting to balance-up consumption and production. While the story told so far of the raw energy potential from renewable sources shows an ecouragingly close race to maintain our rich lifestyles with sustainable energy sources, a little digging provides much disappointment. Between the potential and the realisation lies a factor of over 100! From a production potential of 180 kWh per day per person, we get to an actual production figure of just 1 kwh/d/p and a "realisable" estimate of 18 kwh/d/p---a full ten times less than our consumption. Looking at the heart of the physics problem, David MacKay points to the geographically diffuse nature of renewables: each person needs a huge amount of land, tidal exposure, wind per person to make the sums add up. The sustainable potentials, as David emphasises, need "country-sized solutions". "To get a big contribu- tion from wind, we used wind farms with the area of Wales. To get a big contribution from solar photovoltaics, we required half the area of Wales. To get a big contribution from waves, we imagined wave farms covering 500 km of coastline. To make energy crops with a big contribution, we took 75% of the whole country." Yet protection of species, habitats, nature, beauty etc. all move the same people who want to reduce fossil fuel dependency to limit the installations. Something will need to give to balance our energy ...

Power consumption per capita, versus GDP per capita,

Figure 30.1 (p231)

The only notable ex- ception to the rule “big GDP implies big power consumption” is Hong Kong.

Estimates of theoretical or practical renewable resources in the UK

Street-lights

Moreover, its lifetime is said to be 15 000 hours (or “12 years,” at 3 hours per day)

a little adds up to a lot,” if all those “littles” are somehow focused into a single “lot” – for example, if one million people donate £10 to one accident- victim, then the victim receives £10 million. That’s a lot. But power is a very different thing. We all use power. So to achieve a “big difference” in total power consumption, you need almost everyone to make a “big” difference to their own power consumption.

by reducing our population

Second, to supplement solar-thermal heating, we electrify most heating of air and water in buildings using heat pumps, which are four times more efficient than ordinary electrical heaters. This electrification of heating further increases the amount of green electricity required. Third, we get all the green electricity from a mix of four sources: from our own renewables; perhaps from “clean coal;” perhaps from nuclear; and finally, and with great politeness, from other countries’ renewables. Among other countries’ renewables, solar power in deserts is the most plentiful option. As long as we can build peaceful international collabor- ations, solar power in other people’s deserts certainly has the technical potential to provide us, them, and everyone with 125 kWh per day per person.

Chapter 18 was depressing --- the diffuse nature of renewables in the crowded UK basically means that a realistic view of their usage makes it clear we won't make it on local wind, tide, sun, geothermal, wood etc. Assume: a) we can't change energy per capita too much; b) we can't change the capita (ie no creepy population control) and we still want sustainability ... The basic solution is:  1. electrify transport 2.  electrify space heating 3. produce electricity with whatever local renewables we can, augmented by clean coal, nuclear and imported solar from desert regions. Sounds simple, no?

Figure 20.23. Energy requirements of different forms of passenger transport. The vertical coordinate shows the energy consumption in kWh per 100 passenger-km. The horizontal coordinate indicates the speed of the transport. The “Car (1)” is an average UK car doing 33 miles per gallon with a single occupant. The “Bus” is the average performance of all London buses. The “Underground system” shows the performance of the whole London Underground system. The catamaran is a diesel-powered vessel. I’ve indicated on the left-hand side equivalent fuel efficiencies in passenger-miles per imperial gallon (p-mpg). Hollow point-styles show best-practice performance, assuming all seats of a vehicle are in use. Filled point-styles indicate actual performance of a vehicle in typical use. See also figure 15.8 (energy requirements of freight transport).

So I conclude that switching to electric cars is already a good idea, even before we green our electricity supply.