PV and Storage Heaters

MisteRusty

There seems to be a lot of accumulated wisdom on these forums, I wonder if anyone can help me answer few questions regarding storage heaters ?

I'm installing a 3.9 kwp pv system and am trying to work out how to get the maximum benefit from it.

I'm expecting to use about 50% of what I generate, but since the export rate is only 3p per kw, I would like to increase this as much as possible.

Electric storage heaters seem like a good way of soaking up the spare. However, they all seem to be set up to charge overnight to take advantage of Economy 7 and the ones I've looked at don't appear to allow the charging period to be altered.

I want to be able to charge it up during the day when I'm generating electricity and then allow it to give off heat during the evening.

Does anyone have any experience of this or can give any other examples of how to maximise the benefit from a pv system ?

Premier_2

Storage heaters only usually heat up at night as they are on a circuit that only comes live when off peak energy is supplied.

Don't install them that way and they'll heat up whenever you supply electricty to them

Edit: Which supplier are you with? 3p per kWh seems very low.
Ebico pay 28p per kWh for exported energy produced from pv.
http://www.ebico.co.uk/microgeneration.php

albyota

why would you want to, for example, in the middle of summer, want to dump power into a heater, surely it would be more effective to dump the excess juice in a hot water cylinder using an electric element.

albyota

Its only 3p/kwh for what is exported......they should pay you 41.3p/kWh for every kwh of the electricity you generate.

macman

3p per kWh is the export rate, however you should be paid a variable amount for actual net generation under the Feed-In Tariff arrangements of between 9p and 41.3p per kWh depending on size of system and the date of connection to the grid.
I have a 1.26 kW system installed in 2006, that will pay only 9p. However my supplier (Ecotricity) will top that up to 16p, which is some consolation.
The FIT rate for a PV system of less than 4kW is 36.1p for new builds and 41.3p for a retrofit.

albyota

EMMA (Energy and Micro-Generator Manager)

With the new FIT tariffs EMMA increases the value of over half of the output of your micro-generator by more than 100% and in many cases by more than 500%.


"Surplus" power is used to displace purchased fuel and/or imported power

If you don't use EMMA over 50% of the output from your micro-generator will be exported because of the mismatch between output (which is determined by nature) and demand (which is determined by you). This exported power is only worth c.3p per kWh.. at most. In many cases this is worth nothing. EMMA uses the power that would be otherwise be exported to heat you hot water... thereby displacing fuel or power that would otherwise cost you between 6p and 14p per kWh.

"Free" Hot Water from your micro-generator

EMMA enables you to generate electricity and hot water from your micro-generator. It eliminates the need for solar thermal installations.

http://www.thewebsitepreview1.com/index.php?pid=articles/category_files/emma_home.php&c=36

MisteRusty

albyota wrote: »

why would you want to, for example, in the middle of summer, want to dump power into a heater, surely it would be more effective to dump the excess juice in a hot water cylinder using an electric element.

Quite right. But I have a combi boiler so no way of storing hot water. I'm just trying to find ways of using as much of the electricity as possible.

albyota wrote: »

EMMA enables you to generate electricity and hot water from your micro-generator. It eliminates the need for solar thermal installations.

Very interesting, but at 1100 euros it's the rolls royce solution to controlling a storage heater. I'm really looking for a MUCH cheaper solution.

Premier wrote: »

Storage heaters only usually heat up at night as they are on a circuit that only comes live when off peak energy is supplied.

Don't install them that way and they'll heat up whenever you supply electricty to them

Seems like all I need to do is set an external timer to charge the heater during the hours of peak production. Maybe link it to a light sensor switch so it only charges when it’s sunny?

albyota

OK, I see you point, a storage heater would be fine for the winter...but surely it is unlikely... with the darker cloudy days...there would be much to export.... in the summer however, lighter longer days, a storage heater??? this is the time you would be exporting more, would you need Heat..... unless I am missing something.

albyota

do you have room to fit a small cylinder....loft perhaps, garage etc....?

MisteRusty

Many thanks.

It's certainly true that hot water would be more useful for more of the year. However, I reckon the cost of modifying my combi boiler based system will be in the £000s whereas as 2nd hand storage heater may be less than £50.
Even if it's not running over the summer, my feeling is it's going to be more cost effective, so I think I'm going to go with it and monitor the results. Might wait till the autumn though before I go shopping, and get some better data first !

albyota

have you had quotes for your 3.5kWhp solar PV array yet, if so could you share the info, i.e. make/number of panels, poly or mono, inverter? fronius/SMA etc?