The clean energy future starts now

[Tannin]

In news from Queensland today, we learn that Australia's leading hydro-electric experts from Tasmania will be assisting with the development of a 330MW pumped hydro facility.

The facility will buy cheap off-peak power (typically wind or solar) and use it to pump water uphill into storage. The water is held until power is in short supply, then allowed to flow back through the turbines to generate electricity for the national grid.

Wholesale power prices fluctuate enormously. Power tends to be very cheap at some times of day (overnight, when demand is low and the old-style "must-run" coal plants can't shut down; when it is very windy; or when the sun is shining) and very dear at other times (these days mostly only during the short afternoon peak - there used to be a bigger daytime peak as well but that's pretty much gone now because of all the power generated by rooftop solar).

Wholesale electricity in Australia is auctioned to the national grid. Every five minutes, suppliers bid at whatever price they like, and the grid buys as much power as it needs, starting with the lowest bidders, and paying the same set price to all of them. This price is the highest price bid at the auction and actually used by the grid. It changes every half hour. (There is an averaging system that converts each 6 five-minute auctions into a single half-hour price.)

As a result, the price of peak power can be ten times, even 100 times higher than the price of off-peak power that same day. (Sometimes the off-peak power price is negative! Yes, the generators pay the grid a few cents to take their power because it takes a long time and costs a fortune to stop and restart some types of generator.)

The point here is twofold. First that there is an excellent market opportunity for storage suppliers. Buy power for pennies in the morning, sell it for top dollar in the evening. Money for jam!

Second, that by filling this commercial opportunity, the operators will be doing exactly the right thing for Australia in practical terms. They will be, effectively, selling solar power at midnight and selling wind power on still days. Even if the power used to refill the storage is fossil-generated (which in the main it won't be), it is still reducing cost and carbon footprint because it will be cheap, surplus off-peak power from a large, inflexible generation facility which (by design) can't start up and shut down easily but (also by design) is more thermally efficient than fast-start peaking plants.

Overall, it smooths out the supply cost curve, provides extra reserve peak capacity, allows more effective use of solar and wind energy, and (on average) reduces wholesale prices. And makes a dollar for the investors.

This will be the first of many. Within our lifetimes, there will be dozens of these storage facilities and we will just rely on them without even thinking about it.

More here: http://reneweconomy.com.au/2015/qld-pumped-hydro-storage-project-taps-entura-for-feasibility-study-88148

[HAL]

How much does it cost?

[Tannin]

^ $280 million, HAL. Small change by your standards, no doubt, but still quite a bit of coin.

[HAL]

Enough about me, let's talk about the Pies.

[pietillidie]

Ha cool, thanks Tannic One. Will start reading up on it.

[Mugwump]

Very interesting read, thanks. If its feeder power is via fossil fuels, I can see no great CC advantage, as one is merely storing fossil fuel energy that has already released its CO2. I could be wrong, but I'd imagine there is not that much difference between the fast-start peak generation and base load.

On the other hand, yes, I really can see the positives if it can be fed by renewables when they are on-cycle. That's genuinely exciting.

I guess one question that nags, in that regard, is how the economics work between the PHS system and the renewable feeder system... do you need a lot more PV cells/wind turbines, or whatever, to feed the PHS system as well as supplying routine requirements, or can you do it by using the infrastructure that you'd had have to install anyway - via load balancing, etc?

One more point - I'm no physicist, but I wonder what the energy conversion ratio is - does pushing water uphill consume a lot more energy than you can generate by running it through a turbine on its way back down ?

I was barely aware of PHS, though, and spent some time today looking at it on Youtube - fascinating potential.

[HAL]

If I had more PV cellswind turbines or whatever to feed the PHS system as supplying routine requirements or can you do it by using the infrastructure that you'd had have to install - via load balancing what would I do with it?

[stui magpie]

[Tannin]

Good questions, Mugwump.

Does pushing water uphill consume a lot more energy than you can generate by running it through a turbine on its way back down?

In a word, no. Typical efficiency is about 90% each way, or 80% for the round trip, with some of the latest plants claiming close to 90% round-trip efficiency.

If its feeder power is via fossil fuels, I can see no great CC advantage, as one is merely storing fossil fuel energy that has already released its CO2.

There is still an advantage even with fossil fuels, though it is of course smaller.

For simplicity, let's divide fossil generators into three categories. (I'm going to over-simplify a bit, but that shouldn't matter much to our outcomes).

• Old-fashioned base load plants. These have to run all day long. They take hours or even days to start up and shut down, so they generally run 24x7, shutting down only for maintenance or perhaps during low-demand times of year. Once running, their fuel (usually coal) is going to be burned whether you are using the power or not. So, at three o'clock in the morning, you might as well use that power to pump some water up a hill. (Most nuclear plants are similar, though they aren't burning much fossil fuel, of course, and they generally take even longer to start up and shut down. Note, by the way, that nuclear power is lowish carbon, certainly not zero carbon.) Typical thermal efficiency for fossil base load plants is is 30-40%, with the remaining 60-70% of the fuel wasted. Nuclear plants usually run on the wrong side of 30% because, for obvious safety reasons, they can't afford to use the higher steam temperatures and pressures that the best fossil plants use to get better efficiency - but in the case of nuclear plants, that doesn't matter so much as they are not burning anything.
  
• Peaking plants. These are designed to start up and shut down at short notice. Typically they burn gas using a gas turbine - essentially the same thing as an aircraft's jet engine. The gas turbine is about as efficient as a base load station's steam turbine (30-40%) but the fuel costs a lot more, so they generally only operate during peak periods when the wholesale power price is high.
  
• Load-following plants fall in between those two extremes. Usually gas fueled, they can start up and shut down (or at least drop back to a low fuel burn mode) moderately quickly and tend to run for longer periods than the dear-to-run peakers because they use a high efficiency combined cycle setup: a gas turbine (30-40% efficient) exhausts into a steam turbine which extracts extra power for a total efficiency of better than 50%. But they are very expensive to build.
  

So, if you are pumping water uphill with a peaker, you have rocks in your head! (Unless there is a temporary nation-wide power shortage, perhaps because of equipment failure in a large generation plant taking it off-line, or because daily peak demand is temporarily too high for the system to satisfy even with all stations operating (that is most unlikely here in Oz, we have oodles of surplus generating capacity), or because of a failure in the interstate grid links.)

You'd only want to pump water up a hill with a base load station if you had no other use for the power - you can't just switch them off so you might as well use it.

You might want to do it off-peak with a high-efficiency load-following combined cycle plant on the basis that, even after losing some through the uphill-downhill pumping cycle, it could still be cheaper and more efficient than firing up an expensive peaker for the evening demand. (You'd have to do some careful sums to figure out if this was worth it or not. It would probably depend on the individual case.)

And, of course, you'd always want to use any surplus wind or solar power.

[Tannin]

[Tannin]

[Tannin]

https://xkcd.com/556/

[stui magpie]

Why am I not surprised you're an XKCD fan?

I also like the what if page. http://what-if.xkcd.com/

[Tannin]

^ It bends my head.