Ben@Forest wrote:I've read an article which, taking the author's house in New England as an example, stated that in a worst case scenario it would take 29 years to 'pay back' the fossil fuel investment in making the panels. Annoyingly he doesn't say what the best case scenario was!
Of course conventional ways of creating and delivering power are also fossil fuel dependent and he was pro solar panels, just noting they weren't a silver bullet.
That'll be this
It's nonsense because his estimate assumes that the cost of the solar panel is equivalent to the energy used to make it, his calculations say that if the panel costs $150 and energy is $0.165 per kwh then the maximum energy used is 9.1MW
That's not even close.
Some obvious facts - that solar panel doesn't cost the producer $150, nor despite his best estimates are the raw materials free and wherever they come from someone is marking them up. Nor is the actual cost of energy the same as what he's paying that's also marked up.
My understanding of the process of making solar panels suggests it's a energy intensive process not dissimilar to making glass so the power used is in the order of a few KW per square meter.
The energy payback for solar panels by my overly conservative guestimate is no more than a few months. If it was a year I'd be fairly surprised and would want to see how it was worked out.
What he's really talking about is how long the payback for him personally is based on cost rather than the energy cost payback.
With no subsidies the payback typically for a 4KW installation would be about 10 years and with whatever the current subsidy is it'd somewhat less.
What's worth pointing out is that the payback drops off with installation size since most people would only use 4KW intermittently, my house with all the gadgets ticks over at about 400w so a pair of 250W panels would be in full use all the time and so would have a decently short payback period whereas any panels over that only get periodical use so I'd end up providing cheap (i.e. free) energy to the grid for most of the time.
If you have an electric car and the capability to grid-tie it then you can store that extra power and use it when you need it, payback drops then to nearer 3 or 4 years (I assume the car exists anyway so it's cost doesn't matter).