Solar panels and payback

Not if you included all the other crap you need to make a 'renewable' grid work reliably,

And its the renewable shills who are in fantasy land. Not the nuclear power contingent

Converts solar DC to mains voltage AC.

Tim

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.

Greens are nuts.

That's not the point. If I have solar and a home battery, the battery allows me to gather up enough solar to keep me going during the evening and hours of darkness. eg if my daily consumption is 13kWh and I have a 13kWh battery, with enough solar panels I can generate that 13kWh during the day and need take nothing from the grid.

I can make it to generate that 13kWh only in peak summer or in the depth of winter - it just depends on how much I can/want to oversize the solar system. Through-winter oversizing is probably not practical for most people (they don't have enough roof) so it's just a case of how early/late in the spring/autumn will be covered, versus how much to spend on hardware and how much is practical in their particular property.

If you can handle the daily variations with local batteries, you don't need to call on any peaker plants when everyone is cooking their tea in the evening. You're then only importing from gas plants in the winter period when the solar output is limited.

That avoids all the inefficiencies you state with warming up gas peaker plants. And in the winter you can charge the battery up from the grid when energy is cheapest to flatten out your demand, even when there's no solar output.

Theo

I’m not sure your last point is fully valid.

The winter before last had three separate periods of about ten days to two weeks each, where gas was supplying about 10 to 12GW more than the reliably unreliable renewables.

But it would not have been the answer, because there simply wasn’t enough energy available to recharge the batteries before the next winter blocking high kicked in.

10GW of energy gap for (say) ten days is 2.4TWh. How large an area would a battery farm of that capability cover? How much would it cost?

We were discussing home batteries, not grid scale ones.

Even if the grid is 100% gas, there are still peaks and troughs. People cook their tea at 6pm but they don't cook very much at 3am. So charging the home battery at 3am and discharging it at 6pm saves having to run an extra gas peaker at 6pm.

The same would happen if the grid was 100% nuclear - you really really don't want peaker nuclear plants, so it's better to spread the load out using home batteries than it is to build extra nukes.

In practice, there's often spare renewable energy (not necessarily 3am, but whenever the front passes over) so the more kWh you can get from that the less kWh of gas you have to burn.

Yes you still have to build the gas plants but you don't run them 24/7, you just run them in weeks when you need them and so only pay for the fuel when you need to burn it. As we have already been doing with coal plants.

Theo

I never said you did. Cheer up, I'm (usually) on your side! :)

It feeds our house and the neighbours in parallel with the grid. Presumably for power to flow outwards the voltage must be higher than the mains.

I don't have a battery.

That's not strictly true. If the output voltage is lower that the supply then the generator/inverter power factor lags, if higher higher then it leads.

You don’t need ‘peaker’ nuclear plants, you use any surplus electricity to e.g desalinate water, pump water up hills, generate hydrogen for some strange reason, or flog it to becalmed Denmark.

Using real-world data, I did to death gas as a backup for the reliably unreliable renewables earlier in the thread, in the grounds that it would be more efficient not to build renewables in the first place.

The Irish Republic did a study of their gas and renewables, and similarly discovered it was more efficient to run their CCGTs flat out, while exporting the renewables to the energy-short UK, presumably at inflated prices.

There was a wind turbine fire locally a few weeks ago, the fire crews were there quickly, but had to stand around idle until the owner finally turned up and isolated it. By which time it was just a charred ruin. Having a battery in every loft is a seriously ungood idea.

Wind turbines don’t have batteries hence a wind turbine fire has NO relevance to domestic batteries. So why try and make a connection?

Lithium Iron phosphate batteries are probably lower risk than many domestic electrical appliances.

Tim

The connection, which you seem to be unaware of, is the procedure used by Fire Brigades when dealing with electricity generation, such as standing about watching the conflagration while waiting for someone to make it electrically safe to squirt water on.

Water…electricity…bad mix…

The salient point, then, being that if the householder says there's a battery in the loft, the FB will just twiddle their thumbs as your house burns down?

Unlikely. My battery would only provide 51v - far less than mains voltage and they don't expect that to be turned off. Turbines will have avery much higher voltage output and be coupled to a simialr high voltage line.

What they used to do was wait while a specialist officer also drove to the scene of the fire to assess the risk to the crews, so it’s much as you suggest.

In the case of solar panels they now squirt black goo over them to stop them generating.

It's not the voltage that is the problem but the energy stored in the battery.

What happens if the battery is shorted?

Also 50 volts can be lethal.

I believe new regulations* state that batteries for solar etc. cannot be fitted in a domestic property loft, and when fitted within house they may/will have to be within a fire containing enclosure. Fitted in a garage is probably OK. Some aspects of battery fitting may now come under building regulations as well as electrical regulations.

Fitting batteries under the stairs may not be a sensible option :)

NOt to a human