Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

The Australian Government’s domestic solar PV subsidy…

The federal government has recently announced it will scrap the unpopular means test for the federal subsidy for domestic solar PV arrays, which restricted the rebate to households earning less than $100,000. The size of the rebate was, formerly,$8 per watt of installed nameplate capacity, up to a maximum of $8000. The rebate will now be smaller;$5/W, up to a maximum of $7500. Sounds good, right? But it’s horrendously expensive – the government is in effect paying$5/W for the cheapest, nastiest polycrystalline silicon PVs on the market.

There are scores of companies jumping on the bandwagon to sell these little 1-1.5 kW rooftop PV systems, advertising and promoting and installing them – because they’re making a fortune from the increase in business resulting from the subsidy.

The government rebate does not cover the full cost of such a system – therefore, in order to get as much interest as possible, the vendors are trying to keep the costs of such systems as low as absolutely possible, so that the cost that the customer pays is as small as possible. Therefore, all such systems are exclusively cheap, inefficient, basic polysilicon devices. After all, an advanced solar-concentrating collector with a high-efficiency CdTe cell or stacked heterojunction cell or sliver cell or whatever does not attract any higher subsidy than the basic polycrystalline Si device.

Advocates such as the Australian Greens say that such a scheme “supports the solar industry” – but all it does is supports the environmentally-damaging low-cost manufacturing of polycrystalline silicon in China, and doesn’t support innovation in advanced PV technology or anything like that.

What if the same amount of subsidy might be better spent elsewhere? Here’s a hypothetical idea to think about.

1. Go and find a suburb or a city or a community which has about 31,000 households. I’m certain there are 31,000 households in this country who support what I’m about to elucidate.

2. Get each household to put up AUD $1200 or so, temporarily. 3. Take that 25 million US dollars and purchase a 25 MWe Hyperion Power Module, or something similar. 4. At 25 MWe divided between 31,000 households, that’s a little over 25 GJ per year, which is a little more than Australia’s present average household electricity consumption. This doesn’t just generate a fraction of your household electricity needs – it generates 100% of it, and there will be no more electricity bills. 5. That corresponds to a nameplate capacity of 807 watts per household. Since the government hands out a subsidy of$5/W for solar photovoltaics with a 20% capacity factor, they should hand out $22.50/W for nuclear energy with a 90% capacity factor, right? 6. Collect your$18,157.50 rebate from the government. Less the $1200 investment, that’s$16,957.50 immediate profit in your pocket. This is exactly the same rate of payment per energy produced that presently exists in the form of the PV subsidy.

7. Go to the pub. Got to stimulate that economy, you know.

I wonder how many ordinary Australian households would support nuclear energy if you paid them $17,000 for doing so? To replace one Loy Yang type coal-fired power station* with solar cells, we would need 6,082,342 homes equipped with 1.5 kW solar photovoltaic arrays. With an$7500 rebate for each one, that would cost the government 45.6 billion dollars per each large coal-fired power station.

* (Loy Yang generated 15,995 GWh in 2006.)

Solar photovoltaics typically have a capacity factor of about 20%, and we’ll suppose the panels have a lifetime of, say, 30 years.
Therefore, this scheme costs the government 9.5 cents per kWh generated.

If the government purchases nuclear power plants, they will cost, say, 10 billion dollars (let’s be conservative) for a nuclear power plant with two 1100 MW nuclear power reactors which will operate with a 90% capacity factor and a lifetime of 50 years. The capital cost of plant dominates the overall cost of nuclear energy.

Therefore, the nuclear power plants would cost the government 1.15 cents per kWh – 12% percent of the cost of the solar rebate scheme. That’s the government’s rebate alone – without the rest of the price of these systems.

All this solar rebate is is another mendacious political enterprise involving renewable energy which can’t be scaled up, which hands out free money to the public, makes a bunch of money for the solar panel vendors (including many dangerous fossil fuel vendors such as British Petroleum), and mendaciously makes the government look like they’re actively getting the country running on clean energy.

ASIDE: I’m going to start cross-posting some blog content on the Daily Kos. I think it’s a nice site to engage with many, many readers – many of whom perhaps aren’t already so convinced of the virtue of nuclear energy – so, there’s plenty of engaging, active discussion, and the opportunity to maybe convince some people – even if that’s just a few people it’s still a very positive thing.

Written by Luke Weston

December 18, 2008 at 6:43 am

Thermodynamics, stars, uranium, life and everything: Part I

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We hear a lot about this phrase “renewable energy” these days. But what exactly is “renewable energy”?

Why are certain energy systems considered “renewable”, whilst others are not? What makes, say, solar power “renewable” energy, but nuclear power not, supposedly, “renewable energy”? These questions bear thinking about.

Now, uranium is technically a finite mineral resource, just like the bauxite used to construct wind turbines is a finite resource and the silica used to construct silicon photovoltaic devices is a finite mineral resource from the Earth.

Five billion or so years from now, the hydrogen within the Sun’s interior will be exhausted, and it will begin to use that in its less dense upper layers. It will expand to eighty times its current diameter, about 7.5 billion years from now, to become a red giant, cooled and dulled as a result of its vastly increased surface area. As the Sun expands, it will swallow up the planet Mercury. However, Earth and Venus can be expected to survive, since the Sun will lose about 28 percent of its mass, and its lower gravity will send them into higher orbits. The Earth will be left scorched, its land surface reduced to the consistency of hot clay by a flux of solar heat a thousand times more powerful than that today, and our atmosphere will be stripped away into space by a now-ferocious solar wind. Not one living cell on this planet will remain alive.

Eventually, the helium produced in hydrogen fusion in the Sun’s outer regions will fall back into the core, increasing the density until it reaches the levels needed to fuse helium into carbon. A “helium flash” will then occur; the Sun will shrink abruptly to slightly larger than its original radius, as its energy source has fallen back to its core. Due to the increase in the reaction rates, due to the increased temperature and pressure at the stellar core, and the smaller amount of helium compared to hydrogen, the complete helium-burning stage will last only 100 million years. Eventually it will have to again resort to its reserves in its outer layers, and will again attain a red giant form. This phase lasts a further 100 million years, after which, over the course of a further 100,000 years, the Sun’s outer layers will fall away, ejecting a vast stream of matter into space and forming a planetary nebula.

Eventually, all that will remain of the Sun is a white dwarf, a hot, dim and extraordinarily dense object; half its original mass but only the size of the Earth. Were it viewed from Earth’s surface, it would be a point of light the size of Venus with 100 times its current apparent luminosity. Eventually, after trillions of years, it will fade and die, finally ceasing to shine altogether.

Why is geothermal energy produced by the $\mathrm{\alpha -decay}$ of uranium in the ground considered as “renewable” when that produced by fissioning those same atoms in a reactor is not?

The answer, of course, is that that’s not the point. The point is that “renewable”, as we hear the term used in society today, doesn’t have any rigorous physical meaning. Loosely, the popular definition of “renewable” means “not fossil fuels and not nuclear energy”, and fossil fuels do not meet the above definition when used at today’s consumption rates (if oil use were cut by a factor of 100,000, it would also be renewable). More correctly, “renewable” energy has come to refer to anything that the Green lobby hasn’t chosen to oppose – anything except fossil fuels or nuclear reactor-derived energy. (Nuclear geothermal energy seems to be OK, though.)

When something does meet the definition that the environmentalist lobby doesn’t like, they amend the mysterious unwritten non-scientific definition to exclude it.

For example, whale oil could produced by farming whales, constituting “renewable biofuel”, in exactly the same way that sugarcane-derived ethanol is in principle a “renewable” fuel. I can’t see the capital-G Green lobby being too keen about the idea, though.

Now, it seems reasonable to argue that, for example, wind energy or solar energy are not in fact consuming any significant finite resources at all during their ongoing operation, the raw materials such as aluminium, silicon or concrete used in the construction of their infrastructure not withstanding.

Opponents of nuclear energy often seem keen to point out that nuclear fuels are what they often describe as “finite, nonrenewable” resources. However, there’s no such thing as a source of energy that we can use without consuming any finite resource, because the energy that we can extract from any isolated system is in itself a finite resource. When the free energy of the universe is expended, the “heat death” of the entire universe is the result. This is the end of all that is, all that was, and all that ever will be, and this is going to happen.

There’s no such thing as “renewable energy”.

The free energy of any isolated system, for any reasonably literal, sensible definition of the word renewable, is not “renewable”.

“Renewable energy” does not exist. That’s the second law of thermodynamics.

Written by Luke Weston

October 12, 2008 at 12:58 pm

Some thoughts on the economics of domestic solar photovoltaic installations

Let’s say that 1 kW of solar PV nameplate capacity installed on your roof costs about $12,000. The figures that I’ve seen quoted around are typically$13,000-$12,000 for a 1 kW on-roof PV array installation. (These are Australian-centric quoted costs, in Australian dollars, by the way). With the rebate of$8/W for installed PV capacity (capped at $8000) offered by the government to encourage decentralised household generation, that’s$8000 offset from the cost of the 1 kW system.

With this incentive included, that’s $4000 you need to pay for such a system. Now, based on realistic capacity factors for such a PV system, 1 kW of nameplate power capacity will generate about 5.1 kWh energy in total per day – The PV installation industry expresses this overall capacity/availability factor as “peak sun hours per day” for any given location. The 5.1 kWh is the actual figure quoted for Sydney, Australia. Household electricity consumption in Australia is 7 MWh annually in Australia, according to EnergyAustralia. That’s 19 kWh per day. A 1 kW solar PV installation is just not enough to completely offset your electricity bill and start making money off it. The typical electricity cost to the domestic customer is about 14 c per kWh. It has been proposed, however, that the government could see the price paid for electricity sold into the grid from these decentralised household installations fixed at an elevated price of 44c/kWh At a feed-in rate of 44c per kWh, that’s$820 dollars per year offset from your electricity bill – so, the solar PV installation takes just under 5 years to pay off. If you’re selling the electricity at the same rate that the domestic customer buys it at, 14c per kWh, it’s over 15 years.

However, suppose you want to consider the case of installing enough capacity to completely satisfy your household electricity needs, so that you can be making money of it all together.

(This all assumes that you’re an “average household”, presumably with several family members in the household, and “average” levels of electricity efficiency)

You’re going to need a system with 4 kW of nameplate capacity.

How much will that cost – well, we might assume that it can be done for cheaper than $48,000 – I don’t know, really, so I’ll just guesstimate$45,000. (Some economy-of-scale is to be expected, but I am not an economist, and it’s not an area which I’m familiar with in any real detail.)

Less the $8000 rebate, and that’s$37,000.

Now, you’re generating 20.4 kWh per day, and and consuming 19 kWh, with 1.4 kWh sold back into the grid at 44 c per kWh.

In this scenario, no overall electrcity purchasing is required – so overall, it’s a revenue source.

That’s $225 per year from selling the electricity, plus$971.5 saved from not having to buy the electricity that you use.

$37,000 /$1196.5 gives you a payback time of 31 years. In all likelihood, that will exceed the working lifetime of the photovoltaics.

With the government rebate of $8/kW capped at$8000, going over that amount gets a whole lot more expensive rather quickly.

Written by Luke Weston

April 30, 2008 at 9:08 am