Solar PV with storage heaters - possible?

[maxds]

Hi,

I've had my solar PV panels running pretty well all Summer but now Winter is closing in I'm wondering if anyone has achieved the following:

1. I would like to install a storage heater to load up during the day and trickle feed warmth out during night and early morning.
   The advantage as I see it is that a (hopefully large) element of the stored heat will have come from electricity generated by my panels.
   Obviously not much will be fed back to the grid but I still get paid a portion so that doesn't bother me.
2. Ideally I should like to have the storage heater only draw current (whilst warming up the blocks) when the current generated by the PV panels reaches some limit
   This is so that I don't end up paying a huge bill for electricity from the grid - particularly on cloudy days.
   It sounds like a big ask, since how can this info be relayed to the storage heater controller?
3. I'm confused by the regs that suggest this storage heater needs a separate spur from the fuse box ? why a spur and do I have to?
4. If any one has achieved this, what wattage heater should I pair up with my 2.0KWH peak system?
5. Finally and perhaps more importantly - will there be enough solar PV electricity generated in the depths of Winter to make this setup at all viable?

You can see that this might be a fun setup/experiment but I'm no leccy expert so really need advice.

Cheers,
Max

[Designer_Mike]

Just say NO

Not even remotely feasible.
It makes zero sense.

You are FAR better off feeding power back into the grid (100% efficiency) and then if you want, using electric heaters to heat your house.

IF you wanted to heat a thermal storage device, you would be way ahead to use solar water heaters running upward of 70% efficiency to heat water directly instead of using PV panels (less than 18% efficiency) to generate electricity and then wasting more efficiency trying to heat some bricks or water.

Heating a thermal storage device with PV panels and then trying to extract that heat efficiently is worse than heating your house with electric baseboard heat.

Sorry....but not a good idea.
A 2 KW system ....will generate...maybe 30K btu in a decent day without taking the inefficiency of storage and other losses. That is approximately the equivalent energy of 1 QUART of heating oil if you burn oil for heat.

[russ]

Mike is 100% correct - operating an electrical heater with solar PV power is a very big loser.

Far better to install a solar thermal system for that kind of thing but calculate how many kW of heat you are going to require and how many panels are required. It will give you sticker shock.

I wouldn't go so far as 70% efficiency for solar thermal but 50% plus is quite achievable - a heck of a lot better than the less than 15% for most PV panels.

[Sunking]

1. I would like to install a storage heater to load up during the day and trickle feed warmth out during night and early morning.
   The advantage as I see it is that a (hopefully large) element of the stored heat will have come from electricity generated by my panels.
   Obviously not much will be fed back to the grid but I still get paid a portion so that doesn't bother me.

There is the major flaw in your logic. You cannot control where the energy goes in a grid tied system. If you do this the power will come from the grid at your expense and one heck of an expense which will teach you a very expensive lesson you will never forget.

[maxds]

Hi, thanks for all the replies. Looks like it's a non starter
Just for the record though, the system doesn't work quite the same over here.
On a retro fit (to an existing house), the installer introduce just one new meter that records the kwh generated,
There is no meter that records how much was fed back into the grid, instead the supplier estimates that 50% of the elec generated would have been fed back in and pays in accordance based on that estimate.
Consequently if I use every watt and the grid gets nothing, I still get paid - that will all change when they install a meter measuring output - but I'm not holding my breath for that one.

I half thought, if I could only power devices when the panels are producing then I'd have a truely free source of energy.
I was thinking about an electric car, charged up during the day for example. True wouldn't go far in Winter.

[dogsbody]

In fact I have been thinking on similar lines... The storage heater system is pretty poor when they are heated up on night rate, discharge themselves during the day leaving the evening with no heat....

I have been thinking of a heat pump, storing the heat in latent heat storage with a minimum 12 hours discharge rate.

As based in the UK, regretfully the lack of sunlight during the winter months, coupled with limited output, there just would not be enough to charge the heaters anyway. But the idea to heat during the day to discharge at night is bang on.

[Sunking]

But the idea to heat during the day to discharge at night is bang on.

You are dreaming Green Dreams Rhetoric. The conversion losses are horrific and would only add more carbon silly and get deep in your pockets. Do the math.

It works like this. I pay $1000 today and tomorrow I cash out $250. I will make up for the losses by volume of loosing more money tomorrow.

[dogsbody]

As retired thermodynamic chemist I am well aware of specific enthalpy, and of latent heat storage system which interestingly are used in many telco masts to prevent equipment overheating, and of course servers farms, which allow the internet to function.
The thermodynamics add up. Unfortunately some of the chemistry in heat storage systems suffers from ageing,and dont add up at the moment.
If you look for example on the Mexican adobe wall, the system is ideal. It heats up during the day and releases the heat at night. Simple?

[Sunking]

As retired thermodynamic chemist I am well aware of specific enthalpy, and of latent heat storage system which interestingly are used in many telco masts to prevent equipment overheating, and of course servers farms, which allow the internet to function.

Telecom is my specialty, and where equipment and cooling is concerned money and energy needed is of no concern. Whatever and how ever much it takes is what it is. We design on 300 watt/per square foot of floor space. Roughly 500 times more than a home. So money is no object.

[Mike90250]

http://www.builditsolar.com/Projects.../solarshed.htm Is an idea to start with, for collecting heat