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So I'm not sure how familiar you are but solar and wind are intermittent energy sources. Particularly solar peaks around noon while usage peaks in the morning a
by IkmoIkmo 11y ago
So I'm not sure how familiar you are but solar and wind are intermittent energy sources. Particularly solar peaks around noon while usage peaks in the morning and evening, and around noon when everyone is at work, usage is relatively low.
So you've got an issue, you generate a bunch of energy that's not being used, so it's thrown away. That means the effective cost of an average kwh of solar electricity goes up a lot because you're not just paying for when you're using it, you're also paying (not really, but in a way when you average it) for electricity that's generated and then wasted. i.e. if I build a machine that produces energy for $1 per unit on average, but half my units are generated when I'm not there (and wasted), my actual average cost per unit of energy is $2. The $1 may be competitive with non-renewables, but because half is wasted, the actual $2 price is not.
But of course you don't have to waste it, you can store it, but then you need large amounts of storage and that's not easy or cheap. Take the Tesla powerwall for example, roughly has the capacity to run 1 clothes washer + dryer cycle, and it costs $3k (and doesn't last forever, either). Paying for battery storage for everyone (for when renewables are a big part of total energy production), would put the cost in my hypothetical example somewhere between $1 and $2.
For the actual data (rather than my silly numbers above) you're better off using google, there are a ton of studies that look at the kwh premium when running storage in different contexts. A quick back of envelope calculation for example for home-consumer storage prices... the above powerwall, $3k, lifetime of around 3500 cycles, at 7 kwh capacity, you're talking about the ability to store and use about 24.5k kwh of electricity at a cost of $3k before the device dies, or 12c per kwh. Now 12c per kwh is roughly the average price of a kwh in the US, so a powerwall essentially doubles the cost of of any unit of electricity you want store (the excess power solar generates around noon which can become very significant if we increase renewables a lot). Doubling in price for those kwh is massive, on average it makes little economic sense. In Hawaii, it makes total sense because prices of electricity are much higher. But this is a consumer solution, utility scale is cheaper, and some things can be much, much cheaper (like pumped hydro, way cheaper than a powerwall in general, and way way cheaper if you've got the natural resources like Norway does to build cheap pumped hydro capacity).
So why not turn off the power plants (e.g. coal/natgas) when solar production is high at noon? Because these plants can take 24-48 hours to startup, they provide base power and you can't just shut them on and off.
So yeah, storage is essential and it's not quite there yet. Battery tech has always lagged behind, and now we need it at a massive scale.
- curiousphil 11y agoCouldn't this low demand peak noon energy be used to power something of value to someone somewhere? Perhaps a folding at home type setup? Maybe its a distributed cloud computing platform of some sort? I would think there are many clever ways that this low demand power could be used to generate some income that offsets the price.
- IkmoIkmo 11y agoFor a small village with excess solar capacity, absolutely, a university in a nearby city could choose to negotiate a PPA with the village's solar entrepreneurs and build a datacentre there using the electricity. But if you want renewables to make a difference worldwide and go from 1% of electricity generation to say 30%, then you're going to need such applications on a global scale. Right now there simply aren't such applications, evidenced by the large differences in the price of electricity throughout the day which means there's no arbitrage opportunities available to smooth that out. The most likely arbitrage factor will probably be the rise of electric cars which will provide a natural, decentralised, consumer-driven battery storage on a large scale. Cars are idle most of the day, e.g. when you're at work at noon and solar generates peak power, they can be programmed to charge when prices are low, and at peak times prices would be pushed down due to extra supply.