RE: Dalian battery3 Mar 2021 14:27
This is a very interesting angle on the whole Dalian battery project.
Initially it makes it sound like the Heat pumps are dealing with a problem of overheating in the VRFB batteries - i.e. it is taking the heat away from the battery and is getting rid of this 'problem' somewhere else, like a river or cooling tower. Given the fact that the Dalian Battery is actually right next to an old coal fired power station, which indeed has an existing cooling tower nearby, you might be tempted to think that this is the result - heat pump solves battery cooling problem.
However this is completely missing out on the incredible Coefficient of performance of the Heat pump of something like 10. i.e. that for each joule of electrical energy used to run the heat pump 10 joules of heat are produced at the point you want it. Bear in mind that a traditional ground sourced heat pump has a COP on between 3 and 4 in the UK and an air source HP typically 3 or less. How is it then possible that this heat pump produces a COP of 10 - the answer is that it is taking in heat at a much higher temperature than the usual 5 deg or so of the ground - perhaps 25-30 degrees from the flowing liquid electrolyte in this application - and then generating the 50-70 deg C that domestic heating and hot water systems need to provide a nice toasty shower and building warming with rather conventional radiators.
And the best thing is that it is doing this using the otherwise wasted heat from the battery that would otherwise be having a negative effect on the battery round trip efficiency. Thus this VRFB may be initially trying to store 10 joules of electrical energy, but may only return 8 joules of electrical energy, because 1 joule of electrical energy goes into heating the electrolyte. This 1 joule of electricity can then be turned into another 10 joules of heat, with the further addition of 1 further joule of electrical energy.
Thus we put 10 joules of electricity in and get 7 joules back in electricity whenever we like plus another 10 joules of heat, most likely spread out during the day.
Apart from the rather obvious point that you are getting peak shifting and are able to turn 3 joules of electricity into 10 of heat what else makes this such a clever idea ? The answer is that the heat is generated in the power stacks but is then removed by the flowing electrolyte - thus it only needs to be passed over another rather small heat-exchanger in order to transfer its heat to the heatpump system - gone is all the size of a huge ground source horizontal collector array.
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