Solar pod

captainhindsight_2

Hello, I saw these at ecobuild a couple of weeks ago see here

I am looking to get solar pv and thought it may be a good add on and was wondering what people thought of them for storing any unused energy or if you could recommend any alternative.

groovyf

As a combi-boiler owner, I like the idea behind this thing.

username200

Love this idea.

jimmyboy420

Looks good, anyone know the RRP, or how you wire it up? I'm not worried about the plumbing side as my dad is a plumber

zeupater

Hi

Excellent idea, solar thermal ... now, considering that the technology has been around for a while, what exactly is the advantage over a well specified standard thermal system ??

As an aside, are all combi-boilers solar compatible ?? ... I thought that most weren't and that very few were designed to accept pre-heated water .... if so there's a bit of an issue for some .... then again, for PV owners with DHW cylinders all it seems you're getting is the equivalent of controlling (in some way) a 3kW immersion heater, so no proportional control to match heating to generation by the looks of things .... bet it's a little more expensive (and a lot more complex) than a proportional control PV DHW system though .... then again, what's the use of what is effectively only a 100l in-line heatbank in most situations as the heat transfer becomes progressively less efficient as more mains cold water flows through the coil and the store temperature drops ....

Looks good at first, but then you should really start asking the relevant questions .....

We have solar thermal and adequately oversized DHW storage to see us through the odd overcast run of days which is pretty normal in the UK ..... I'd certainly not trade it in for one of these and expect to still have adequate 'free' DHW or save money (whatever the likely cost) ...

HTH
Z

Dave_Fowler

I've been considering something along the lines of the Solar Pod for some time now, as a DIY addition to my DHW system. I have a standard vented system, indirectly heated by the gas boiler and electrically heated by an immersion heater (controlled by the proportional system using excess PV power)

My airing cupboard is rather restricted so fitting a larger tank would take away quite a proportion of the cupboard space. The immersion in the tank heats only the top part of the tank. This is quite good as it provides a supply of hot water very quickly.

But when the family visits us, we have to resort to the use of the gas boiler to heat the whole tank. I know I could have a tank with a second immersion heater at the bottom so that the whole tank could be heated electrically. But the idea of adding a second 100l tank in the loft (where there's lots of space) and then having around 200l of hot water is more appealing.

However, I think the Pod is somewhat over-engineered. Why the use of the indirect heating coil to transfer heat from the Pod to the DHW tank? Surely, if the heated water were drawn off from the top of the Pod and cold water introduced to the bottom of the Pod - just like a standard DHW tank - there would not be a significant reduction in the temperature of the water when half the Pod is cold and the other half hot which would be the case when a heat transfer coil is used.

This leads me on to a question which perhaps someone may be able to answer for me. Can a standard DHW tank be mounted on its side?

Most directly heated tanks have the immersion heater boss at the top of the tank on the side opposite the position where the cold water inlet is placed. If the tank were mounted horizontally with the immersion heated at the lowest point and the cold water inlet on the top edge, all the plumbing connections could be reversed:-

Plumb the cold water in to the centre of what used to be the top and take the hot water out from what is designed to be the cold water inlet. The original expansion pipe would serve as an expasion pipe for both the old and new tanks

Cost for a DIY system - around £200?

If this is considered feasible, I will be investigation an add-on piece of electronics to switch the PV proportional supply from the old tank to the new, once the old tank is fully heated and the thermostat turns off.

Dave F

zeupater

Dave_Fowler wrote: »

I've been considering ...
.... If this is considered feasible, I will be investigation an add-on piece of electronics to switch the PV proportional supply from the old tank to the new, once the old tank is fully heated and the thermostat turns off.

Dave F

Hi Dave

If I read that correctly you're looking at a second cylinder in series ? .... something like Header->NewCylinder->ExistingCylinder ?.

I suppose that the issue would be to ensure that the header tank level would be high enough to ensure that the loft cylinder is fed correctly and to come up with a priority switching circuit for the two immersions (but I'd guess that would be relatively simple) .... the priority would need to be old before new in order to ensure hot water in low irradiation conditions, then when the first thermostat shuts down, shift supply to the new tank which will supply pre-heated water to the existing DHW cylinder .... if so here's a possible product range to look at ... http://www.albionwaterheaters.com/product-horizontal-cylinders.html ... looks like you'd need no coils, an immersion boss and don't forget a vent pipe ...

I've seen similar done with a large single coil cylinder (~250/300l) feeding a smaller twin coil cylinder in a solar thermal system setup where a thermostatic valve controlled the heating priority (we actually considered this setup when we had our solar thermal installed, but eventually decided on a single stratified tall cylinder) ... the twin cylinder solution works especially well in the darker months when there's only enough heat collected to supply the small cylinder, so with your idea sounding pretty similar there shouldn't be too much of a problem but I'd guess that a less commonly available horizontal cylinder would be a little more expensive than normal, so have a look around for prices before going too far in developing the control system.

HTH
Z

Dave_Fowler

Hi Zeup,

Thanks for the link. They're the only tanks that I've found so far designed for horizontal mounting. Screwfix, Wickes etc. only offer standard upright tanks.

There's no problem in my loft in getting a sufficient head to fill the second tank as the header tank sits on a high platform. What I'd like to do is use a standard tank on its side as it's likely to be much cheaper than a specialist horizontal tank. The brochure in your link suggests that immersion bosses are not provided as standard but can be fitted as a 'special'.

Your interpretation of my post is correct, only I'd describe the two cylinders as being in series rather than parallel.

Early days yet - a project for the early summer.

Dave F

zeupater

Dave_Fowler wrote: »

... Your interpretation of my post is correct, only I'd describe the two cylinders as being in series rather than parallel ...

Hi

Actually noticed that & fixed the error pretty quickly (but not quick enough) when reading it back, so changed it when sorting out the post formatting, whilst watching the gogglebox, filling my face and drinking a cuppa ... isn't life complex on a Saturday evening ...

Z