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ASHP v Immersion with PV


Marvin

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Results for us as they come forward...(and not what I expected)

 

Our Cool Energy inverTech Air Source Heat Pump CE-iVT9 4.3kW-9.5kW has been on standby only, for the last few weeks, and I have measured the power consumption. It appears to use about 0.1 kWh an hour. That's about 2.25kWh a day in 24 hours.  

 

We use a Solic 200 to direct our excess electricity produced by the PV to the hot water immersion.

 

Whilst the Solic way of heat the hot water uses more energy, because it only runs using power we would otherwise give to the grid, its better for the bills to turn the ASHP off all together rather than use it to heat the hot water tank.

 

You would think that with a high COP it would be better to use the ASHP but with the other things on in the home and the car being charged, you can never be sure your not buying all the power.

 

Secondly I think the ASHP runs at  a minimum of about 1.5kW when heating the water. The Solic can use any spare power from the PV: 10 to 3000 Watts.

 

We could turn the ASHP off altogether and on only when we need hot water and I have decided this is a bit fiddly so won't do it.

 

Another benefit is the fact that the hot water tank is set to 70C ( the ASHP will only do up to 60 and that is at its least efficient) and this lasts us at least 2 or 3 days before needing to be heated up again! ( We do have a super insulated tank) Days when it could be cloudy and we would have to pay for the power. ( We will turn it up higher in the winter and use it as a thermal store for night time warmth...)

 

1830761436_TankStat.thumb.jpg.0b84874ebe9748abe7a987b6006abb93.jpg

 

And finally I would rather wear out the £50 immersion than the £3180+VAT ASHP!

 

Good luck with your project.

 

M

Edited by Marvin
Steamy tea clarification request

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One of the wonderful things about buildhub is the ability to discuss different viewpoints and ideas without constently bitching at each other. (Politicians please note!)

 

IMHO the grid has 2 main problems: what it uses to produce electricity and what it needs to supply our peak power demand.

 

More renewables will help, however peak demand is the killer. All the renewable power sources in the country will not produce enough power in the winter to forfill our demand. So in winter we use other types of energy producers to meet this demand which sit idling during non peak demand. This is a costly problem!

 

Just Drax's carbon capture plant for example, is going to cost about £30billion - that's £500 per household, and at some point it will already have to sit idle sometime during the year due to excess production from renewables.

 

If I have it right, we already reached the point that we produced as much as we used from renewables at one stage so we're already getting towards over production. 

 

As for the power generation and use, my utopian way would be self sufficiency which presently I/we cannot achieve due to financial restraints. However my aim is to work towards this. The main stumbling blocks for us are:

 

Cost and size of electricity storage on site and lack of power production during winter.

 

Peak demands from home equipment.

 

The lack of power production during winter is the biggest problem because by default the cost of storing the power and size of storage would be extreme for an individual home.

 

We have worked on our home appliances but reliance on ovens, toasters, kettles and the like really require a change of habits. 

 

So as I see it, the cost of peak production is what we will have to pay for, less any renewable energy available at that time, which judging by my winter exporting would be sweet F.A.

 

(By the way the only predictable source of winter renewable energy I know of not being used and  presently available is tidal!)

 

So I expect that the power companies know all this and aim to protect their profits by introducing a way to charge more for power used during winter and or peak demand. (Ho ho! Any guesses how this will happen???)

 

So I for one will be looking at ways to reduce my winter demand and increase my winter supply and storage capability.

 

Good luck to you all.

 

M

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34 minutes ago, Marvin said:

So I for one will be looking at ways to reduce my winter demand and increase my winter supply and storage capability.

 

I look forward to reading about how that goes.

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58 minutes ago, Marvin said:

We have worked on our home appliances but reliance on ovens, toasters, kettles and the like really require a change of habits. 

Yes, there is only so much effficiency that can be got from electro-mechanical equipement.

My two biggest savings have been from reducing heated water temperature and getting rid of parasitic loads, I still get miffed if I leave a 3W light on.

 

I have never done the sums, but DHW energy usage, in winter, could be improved, I think, by pre-heating, even by just a few degrees, the incoming water.  Then boost via an instantanious heater, powered from a PV supplied battery bank.  Really down to where the largest standing losses are, thermal storage or battery efficiency.

 

The easy way to to use a lot less, easy for me as I live alone and take an interest, harder for a family.

Who can put a price on an arguement over the length of a shower.  Well we all can, about 5p/minute for a 10 kW shower.

 

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