OT: Heat pumps

I had one in the kitchen working up to the mid 80s, purchased around

And what do all those wind farms built without any storage require as backup to ride out the short and longer term interruptions to generation? Oh yes, gas!

(since they need gas power stations running in hot spinning reserve to pick up the load on short notice, you have "built in" gas consumption to make wind power useable).

But that's less gas consumption than if you were running gas full tilt - ie it proves the point that supply side can decarbonise where demand side (ie your gas boiler, or gas HP) can't.

Many of those short term interruptions are covered by batteries now, so you don't need as much hot reserve any more - just medium/long term gaps (and the forecasting is pretty good now, so you predict that need a day ahead).

Every kWh that is generated by wind is not quite a kWh of gas saved, but it's getting closer.

Theo

The combined-cycle gas turbine (CCGT) uses ‘waste’ heat from the turbine to provide steam pressure to run a second generator, thus improving the overall efficiency of the system.

During fire-up the turbines are very inefficient, from ~0% for the first 5 minutes, to 25% to about 45 minutes, when the second part of the combined-cycle kicks in at about 60% efficiency.

With 60% efficiency, each GW of power output uses 1/0.6=1.67GW of gas.

Interestingly, if a 1GW CCGT was replaced by a 1GW wind farm, real-world data suggests the latter, over a year, would produce an average of 0.36GW, leaving 0.64GW to be supplied by the CCGT now operating in an intermittent regime of stop/start and throttled-back running in which it might be only

So over the year the CCGT will use 0.64/0.4=1.6GW of gas, which is the same as if it ran in efficient mode and the wind farm didn’t exist, the latter having cost money and materials to no real effect.

Renewables are a waste of resources.

Bless! I think you actually believe that.

-- “it should be clear by now to everyone that activist environmentalism (or environmental activism) is becoming a general ideology about humans, about their freedom, about the relationship between the individual and the state, and about the manipulation of people under the guise of a 'noble' idea. It is not an honest pursuit of 'sustainable development,' a matter of elementary environmental protection, or a search for rational mechanisms designed to achieve a healthy environment. Yet things do occur that make you shake your head and remind yourself that you live neither in Joseph Stalin’s Communist era, nor in the Orwellian utopia of 1984.”

Vaclav Klaus

This newsgroup is probably not the best place to ask this question, but here goes regardless.

What is known about the effect of reducing the ground temperature, maybe in spot locations, that the widespread use of heatpumps may/will cause? I cannot imagine there will be no ecological effects, for instance...

J^n

You got it.

Worse still, the way the market is rigged, there is no point in building an efficient CCGT at all,. Save yer money and build two gas guzzling OCGTs. You end up burning *more* gas.

And then there is the servicing of remote wind farms by diesel boat and land rover...

In town it wont offset the heating from all the other energy the people use.

In the country it might drive the badgers away I suppose.

But the power stations that drive it will inevitably put the heat back

Irrespective of CO2 bollocks, a high human population with a western lifestyle willl always be pumping more heat into the air. and ground...

Let's look at yesterday:

The sun went down - an extremely predictable event, but if it was wind the weather forecast would have told them what the wind was going to do, in aggregate over the whole country.

At 6.30pm gas was 9.63GW and solar was 1.82GW.

So we needed to ramp almost 8GW of gas. On your numbers:

Total extra gas burnt in inefficiency: 2.77GWh

During the past 24 hours, solar returned an average of 3.76GW across the day (including night time), or 90 GWh total.

In other words, if you were using gas alone you'd save the 2.77GWh ramp cost but have to spend 90GWh on gas. (gas also has a fuel opex cost which solar doesn't; solar and wind are mostly capex)

Worth paying 2.77 to get 90?

Wind is a bit more noisy across the day, but batteries are increasingly covering that. In aggregate, over the whole country, a lot of that noise smooths out.

(It is not 'always windy somewhere' as some claim, but that means you don't need to worry about individual gusts - as the storm passes over it'll be windy and then still somewhere, and windy when the next place gets hit by the storm)

Which is why you don't do that - you install more GW of wind than GW of gas.

According to the numbers above, they're a bargain.

Theo

Many, many years ago, I read a science fiction story (it might have been by Robert Heinlein because he tended to use "what if" scenarios) of a planet where everybody used what today is called a ground source heat pump. With so much heat drawn from the ground, it created a permafrost planet and the entire population died of starvation because no crops could grow.

For ASHPs, it's still heat-positive. You put in 1kWh of electricity to move

For GSHPs, most of the shallow ones are collecting heat that has been stored in the earth during the summer and collected in the winter. It's possible that changing the temperature of the ground will have some ecological effects, perhaps due to a cooler ground in the winter. But that would only be local, eg reduced crop yields in the field with the GSHP collector.

For GSHPs with deep boreholes, the heat being collected there is more composed of radioactive decay of the earth's crust (why rocks are hot at depth). This is more like a fossil heat reserve in that it's possible to extract it faster than it's being generated, ie it might become less effective over time. But, since nothing lives down there aside from perhaps very hardy bacteria, I can't see any ecological effects.

Theo

It is difficult to extract more heat from deep sources than you suppose. Most deep botre geothermal installations have essentially cooed the earth around them after about 15-20 years and there is a very slow rate of replacement.

Good example, and it does sound like it could be a Heinlein story. I am not thinking of anything as extreme, but the web of life is very complex, and 'systems bite back' in unexpected ways.

Heat pumps put significant net energy into the environment, even ground source ones would generally warm the planet. Very hard to see how they would cause permafrost.

Perhaps it was about geothermal?

That’s not the point.

Taking your scenario, without solar, there would be no ramp-up costs as the CCGT would be running flat out all the time. All solar had done was to save

In fact, your scenario points up the waste inherent in the use of renewables.

I believe Eirgrid had their mixed gas/wind electricity analysed by an independent organisation, to determine how to run the system most efficiently.

The result was to run their gas generation in the most efficient mode, i.e. flat out all the time, and flog the intermittent wind generation to the Brits.

It’s some time since I last come across this, but I’m fairly sure of the account.

When the wind doesn’t blow, it doesn’t matter how many wind turbines one has, there’s no generation.

Real-world operation suggests that isn’t the case.

It is less gas, but perhaps not as much as you might expect. On shore wind has a load factor of as little as 25%, so you will be using the "back up" generation for 75% of the time. Also that spinning reserve is using some gas just keeping warm and ready. (older style single cycle gas plant is probably better suited to this application since combined cycle will not be able to reach peak efficiency anyway). Off shore is better at 40% load factor.

You also need to include the accelerated wear and extra maintenance needed on the gas plant that is being ramped up and down frequently.

How much battery storage is there?

Prediction helps, on windy days you will be able to shutdown combined cycle plant (although at the cost of its lifespan). However if you predict wrong and it has to start it will swallow about 7 hours worth of run time gas consumption just to get started again.

The main problem thus far is that backup generation and grid integration still seems to be considered as an externality (i.e. somebody else's problem). That makes the price of wind generated electricity look good - but that is partly because everyone else is picking up all the extra costs (not just gas, and plant wear, but also the extra grid connectivity, long distance distribution networks, and let' not forget all the carbon taxes added to bills to kickstart investment in wind)

What seems to be the most bizarre bit to me, is that having cemented in a requirement for gas for the next few decades, why are we not exploiting our own natural gas reserves in the the North sea? Instead everyone seems to be assuming that we will always have reliable and cheap access from other sources. Just look at the state of chaos the world has been plunged into by various "superpowers" in the last 5 years.

The new wind farms are paying for connection costs - or deciding not to for West of Orkney