My ray of sunshine

Off grid--by Dionne Gain, The Age

From Elizabeth Farrelly at The Age:

Although the term “solar system” usually refers to our heliocentric colloquium of planets, asteroids, comets and assorted gravity-tethered junk it could equally designate the arrangement of wires, batteries and photovoltaic panels that hover above my head as I write. I can’t tell you how much I love it, my little solar system.

Each day, rain or shine, it is fully replenished (after its overnight fridge-running duties) before breakfast is done. I can charge all devices, run a fridge and a vacuum - run the heater all day if I like - at zero cost to self or planet. In more than three months, the batteries have never dipped below three-quarters full.

It’s not cutting edge or anything. Slinky, certainly, with a neat box of lithium-ion batteries and a wee animated readout tracking the photons, letting you monitor charge-rate, usage, feedback - even remotely, via app, from a thousand clicks. But it’s not earth-shattering. Not the artificial photosynthesis of which science is now capable. Yet still it strikes me, every day, as a kind of magic.

All this is less evident with urban solar because it’s often just an adjunct to grid-type power, of which the true costs are hidden – dissipated communally and amortised over time. Here in the country things are much clearer. Just to connect, although the poles and wires are easily visible from my desk window, they wanted to charge me $50,000. And that’s before I started paying through the nose for the power itself, at rates increasing with every disillusioned consumer who deserts to solar.

Fifty thousand bucks. My generously proportioned solar system cost less than half that - and thenceforth is bountiful, clean and free.  We can wrench the coal from the ground, burn it in a way that pollutes the air, wastes water and heats the globe, transport it vast distances via wasteful and uglifying wires. Or we can sit with our hands out and silently collect what nature gives us gratis. You can have a clunkety-clunk diesel generator, a filthy coal-fired power station or this sleek and silent on-site engine whose only moving parts are photons in and electrons out. You choose.

More energy strikes the earth in an hour than the world can use in a year. Scientists have calculated that to generate the necessary 15 terawatts of carbon-neutral energy would use only 0.17 per cent of the earth’s surface – a country the size of Venezuela or Namibia. Obviously, this incident energy is not evenly distributed. On the other hand most of it falls on the poorest countries – Africa, India, South America. So my question is this.

Our politicians blather on about how we have to dig, sell and burn our filthy coal to drag the world’s poor out of misery. We’re awfully bloody sorry about climate change, and the island nations we’re drowning, but honestly it’s the only way to end poverty. Blah blah.

Yet Elon Musk says 100 Tesla Gigafactories (producing low-cost lithium-ion batteries) like his Nevada model could “transition the whole world to sustainable energy”. So why wouldn’t they just do that?

Why can’t the rich countries see that ending poverty by driving climate change is madness? That their greatest calling, for themselves, their grandkids and the so-called “third” world is to provide free, clean energy forever?

Why don’t they bundle their aid budgets together and just build these factories, these massive arrays – a hundred, two hundred. Honestly, whatever. Just bloody do it.

[Read more here]

To provide electricity to a home which is off-grid, you require more resources than you would for one which is connected to the grid.  This is because the demand on the grid from millions of consumers averages out.  I don't put my kettle on at the same time as my neighbour.  Similarly, the supply of electricity from renewables also averages out.  The winds in western Victoria blow at different times and strengths to the winds in eastern Victoria.  At any given moment, sunshine levels are different across the state and the continent.  If there are adequate interconnectors to distribute power from one end of the state to the other, the need for storage is reduced.   Moreover, having a mixed supply from wind and solar also means that less storage is needed.  That's hard to do cost-effectively for a single off-grid house, as small wind turbines are much less efficient than large ones. 

Yet, even without being connected to the grid, the author has had no shortage of electricity.  Note that the three months she talks  about (July, August, September)  are the coldest months of the year in Australia, which means that even using heaters she has had enough power to run her house. 

The implication of this is obvious.  If a single household can go off grid, clearly the whole grid could be run using renewables.  This is so obvious that I always wonder that denialists can't see it.  With the right level of storage, with interconnectors, and with some "excess" capacity (see below) we can move to 100% renewables without blackouts.

What about cost?  The author doesn't give the details of the panels and battery she installed, but  6.5 kW of solar panels would cost $4000, and a Tesla 13.5 kWh Powerwall would cost about $15,000 fully installed.  She says the cost of her installation is "less than half" $50,000, so that would fit.  I don't know how much electricity her house consumes, but the average is something like 20 kWh per day, which means that even with only a 13.5 kWh battery she has never run out of electricity.   On the other side, her cost savings would average $4000 a year ($2200 for the electricity and $1800 for connection) -- she will never pay another electricity bill.  And her installation will have paid for itself in 5 years.  No wonder the utility companies are petrified of household solar + storage and say it needs "regulating" because it's "unstable".

Note that 6.5 kW of solar panels would produce far more power than the house needs every day in summer (35.3 kWh in January) and the panels will have to be automatically disconnected from the house's internal power grid to prevent damage and fire.  This is the equivalent of curtailment at grid level.  One way to ensure there is enough power from renewables is to overbuild capacity and then curtail output when supply is greater than demand.  In effect, this is what the author has done on her house.  But this adds to costs, though overcapacity is typical even with conventional power stations in order that all likely demand levels can be catered for.  A future grid powered by renewables would also have inbuilt additional capacity for the same reason.

To get equivalent levels of storage from the grid would mean 16 hours of storage capacity would be needed.  That would add US$70/MWh to the cost of the underlying electricity at current battery costs.  This is slightly more expensive than coal, according to Lazard's LCOE estimates.   But the cost of batteries is falling fast.  In 5 years' time, storage will cost 1/3rd of what it does today.  Which means that 16 hours of grid-wide storage would add just $23/MWh to the cost of electricity.  In other words, still a little pricey now, but cheap in 5 years and even cheaper in 10.