Hi Guys I have not contributed for a while as often feel out of my depth and so content to read along!

Anyway at long last we are about to build an extension to the factory/workshop. We have a 10 kW Turbine and a 10 kW Solar PV installation. When we paid for line upgrade to Western Power we requested they leave provision for 30 kW however they said not possible and gave us 25 kW max. Having spoken to Western Power they are now saying 20 kW is now our maximum export they will allow (without silly money going their way). Our installers are saying if we stick another 10 kW of PV on the new roof the odds are that most of the time we would not be able to go over the 20 kW limit as Sun and wind in perfect harmony a rare event, and if we get close there are gizmos that can be fitted to prevent us going over. We use electricity for light, office, machinery etc. and Kerosene for the boiler. Cost wise we spend not far off £10k a year on kerosene but electricity is down to around £2k so my questions are:

Would, Western Power would allow this?

Is this the best way for us to reduce our energy import? (we did undertake quite a big insulation exercise a year or so back, thanks for the help ST!) but running the kerosene boiler that melts the wax (we make candles) is still our biggest energy user by a mile. I have been advised that Solar would not be hot enough for our needs (boiler runs at around 75C ) but PV could power heating elements to help heat the water system that the kerosene boiler heats.

Are we missing a trick here should we be looking at heat pumps, a new pellet boiler etc?

Any thoughts gratefully received

New pellet boiler - comment. Our local swimming pool installed a pellet boiler, replacing their oil boiler. According to the latest accounts, the non-domestic RHI payments actually cover all the running costs for heating, so that may apply to your situation as a business user. If this does apply, it would seem to be worth checking the figures. We had better leave out any arguments about the sustainability of using wood pellets or we'll be here all day!

More PV panels? If you can mount the new panels to take advantage of early and/or late sunshine, rather than trying for the noon peak, you could find the even spread through the day more useful. I would imagine that using electric heaters to heat the wax, with a boost from the oil boiler when necessary, might be the way to go. I have an inverter with a programmed cut-off at the 16A limit, although my own 4kWp array rarely reaches 4kW output as it is split 3:2 East:South, but it does produce electricity over a large part of the day. If I had known the that large Beech in the back garden would have to come down, I might have installed more panels facing West as well

Hope this is useful

Thanks Mark
I will PM a link for our promo video under 3 mins dont worry (as it in effect promotes a product not sure if I should post it up) not a lot of help but gives you a feel of just how low tech we are! you are right energy was not a real headache 10 years ago but costs I guess have given us all a well deserved wake call.

interesting that we can in effect over install on the PV.

The boiler at nearly 18 years old must I guess be a contender for retirement. as budget is limited we could not fit PV or Solar and a new boiler basically the boiler heats the water which runs round in water jackets round the stainless tanks, 7 tanks each can hold 500 kilos of wax water temp return depends on how much solid wax we are melting down over the day, busy times big drop on tick over very little drop.

Honestly we are very very low tech, our main drawing machine is pre war (and East German) but it is all part of our rustic charm :)

Thanks all, some really useful input. all our roofs are pretty much exactly North/South facing so spreading the angles of new PV not an easy option. right off to try and get my head round Ed's calculator...

Some people would call it a big tub of wax.

Others would call it a phase-change thermal storage installation.

1kg of beeswax absorbs about 150kJ between 40C when it starts to soften, and the melting point of 62-64C. It releases the same amount when it solidifies again. The figure 200-220kJ/kg for paraffin wax, described by Wikipedia as 'an excellent material for storing heat' http://en.wikipedia.org/wiki/Paraffin_wax

Put that another way: you need 24kg beeswax or 18kg paraffin wax to store 1kWh. A ton of wax could absorb 4-5 hours output of your 10kW PV. You have tanks for 7x500kg=3.5 tons wax. If I have done the sums right, the idea is not totally crazy (SteamyTea, I *know* you will check my calcs.)

I don't know what tariff you are on, but if you get paid for generation rather than export, PV might be more economical than solar thermal as a source of process heat. You might need a few more tanks if you seriously intend to pursue a policy of 'melt wax while the sun shines'. They would, of course, need to be well insulated.

Hey, this stuff could make sense even for people who don't make candles

I now have this Willy Wonka vision of an office heating system consisting of a long conveyor belt which carries freshly-made candles, still radiating heat, past every desk.

But seriously, folks. Certainly there is heat to be reclaimed from the candles. I am not sure a heat pump would be economic, or necessary, for this. When you use fans to cool the candles, what do you currently do with the resulting warm air? Is it laden with VOCs or could it be ducted direct to the office? If you need to transfer the heat to fresh air, a simple heat exchanger might be OK. Exhaust-air heat-pumps are used mainly in places like commercial kitchens where they have a big supply of hot air and a demand for hot water - you might qualify, I guess.

Better stop. This is all getting a bit beyond my expertise...

John, have you seen the cloud cover in Cornwall!!

Posted By: rhamduIs it laden with VOCs

Having been to the factory I can tell you it does smell a bit, not unpleasant, but not what you want it your office/showroom.
The main problem would be transferring the the low grade energy between buildings. I like the idea of an A2WHP taking the energy out of the production area and piping it to the office. It is a big production area compared to the current office area.

Really? Any examples of running solar thermal at 230 °C in the UK?

It might make sense with concentrated solar (probably in a sunny country) but for a setup like Candlemaker's this seems, to this humble correspondent, not a very good idea.

A quick calculation shows that with insolation below 900 W/m² the standard Navitron 47 mm panels will not produce any output at all at 210 °C above ambient - the losses from the panel exceed the input.

Of course, this isn't a terribly realistic calculation because it's extrapolating the performance figures way out of the range they're intended to be used in. Still, I suspect it gives a rough idea that really not a lot can be expected. Of course, there are better ETs available but still…

Even at 1000 W/m² they produce very little:

http://edavies.me.uk/2012/11/pv-dhw/#Tout=210&Cco=60000

with the cost per watt being 10 times that of PV. If you actually wanted to heat thermal oil to 230 °C in the UK from solar your best bet would be to do most or all of the job with an immersion heater run off PV.

Last summer I left one of my Navitron tubes out in bright sunshine (with the heat pipe in) with the top wrapped in some impromptu insulation (work gloves then some other bits of cloth then a bin liner as a wind-tightness layer). It got to 195 °C and the plastic bung at the top of the tube browned a bit.

I love the Willy Wonka mental picture not sure the guys would like to be known as Umpalumpa's! just fascinated now with how much heat we waste in production, the fans we use at the moment literally are just big desk fans so they are only stirring up the air not really cooling at all. to give you an idea of just how Willy Wonka we are here is a link to a very short video on how we make them

https://www.youtube.com/watch?v=d397d5q7oNg

Really hope this will not fall foul of advertising rules there are loads of other great candles out there not just ours and candles probably not high on a list of green building products, but if you see what/how we make our candles you can see how low tech we really are!


We are also trying to get a handle on the energy mix of what we use and what we generate as we have a supply meter and two export meters not easy. All are with Scottish Power and when I spoke to them asking if we could have a smart meter fitted the answer was no they are not installing them until they have to.

Just to give you an idea of how sunny it is down here this is a view of the clouds from my window.
http://youtu.be/t9eQnXOQhOg

Still it stops the shadows hitting the PV.