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RV Questions and Answers

My last post on living in an RV has generated a bunch of questions by comment and by email. Instead of responding to them individually, I'm going to answer them all here.

How long did it take you to outfit the RV with solar power?

Putting solar power into an RV is a simple job, primarily because most things in an RV (everything that I use) runs of 12V DC power instead of standard household 120V AC power.

Power monopoly

On Green Thinking

Why does Eskom have a monopoly on the generation of power? The one reason is historic/economic, the other thermodynamic.

Eskom (earlier known as Escom/Evkom) was created 1922 to supply South Africa with cheap, abundant power. It was not the first generator of electricity in the country: Kimberley had electric street lights in 1882, and the Victoria Falls Power Company was an early supplier of electricity to the Rand mines. Electricity was a growth industry, and the government got in on the ground floor. The Transvaal government passed the Power Act in 1910, which defined electricity as a public service. Through the 20th century Escom consistently installed more capacity than the consumers demanded, so that no company could supply electricity at competing prices.

For the thermodynamic reason, consider a thermal power station. In general, it boils water to produce steam, and the steam drives a steam turbine. The steam turbine spins an alternator, which thereby generates electricity. The cost of electricity therefore depends on the cost of the coal used to boil the water and the capital costs of the power station. Over the lifespan of the power station the cost of the coal dwarfs the capital costs. Therefore one will want to get maximum power from a given amount of coal. The technical term for this is 'efficiency'. Since a steam turbine is a heat engine, Carnot's efficiency limit applies, which says that the greater the difference between the inlet and the outlet temperatures of the turbine, the more efficient it will be. Since the outlet temperature is determined by the temperature of the cooling water (and can't be lower than freezing) the astute engineer will design his steam turbine with an inlet temperature as high as possible. Efficiency is also impacted by thermal losses. Thermal losses are minimized by making the boilers and the turbines as big as possible to minimize the surface to volume ratio

So the engineer that designs a power plant to supply millions of people with cheap electricity will design a big, hot system. A big, hot system is expensive to build, so enormous amounts of capital is needed. This pushes small players out of the market. Even municipal generators eventually realize it will be cheaper to buy from Eskom than to generate their own. In this way, thermodynamics drive electricity generation by steam towards monopolies.

On a green note: Photovoltaic power generation is different. Since no solar panel is significantly more efficient than another, a large number of small players can effectively compete.

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