Talkin' 'bout my generation

As any solar pv system owner knows, more generated electricity is usually exported to the grid than is used around the house. Even on dull days at this time of year, we are generating more than we use during the average day. With affordable storage solutions still a way off and our export payments deemed at 50% of total generation regardless of how much we actually wave bye-bye to, we were left with three options:

1. Do nothing.
2. Get an export meter installed (probably at some cost) and get paid accurately for everything we export, rather than the assumed 50% of total generation.
3. Use as much of the generated electricity (usefully!) as possible, while still getting paid for the assumed export of 50% of total generation.

1. & 2. were quickly discounted on the basis that we were buggered if we were going to give away our lovely, fresh, organic electricity for free, or at some discounted rate, just so that we could buy a load back again in the evening at three times the price. Option 3. it is then: Use as much, usefully, as we can while still receiving export payments for half of it, whether we export or not (I stress the word 'usefully' again - tempting as it is to waste as much as possible just so the energy companies have to pay us for nothing, me no like waste).

The usual way to use up a surplus of electricity is with one of many devices now on the market that dump the excess to an immersion heater, to provide hot water. Such devices monitor export and, by controlling the power to the immersion heater, never use more than the available surplus.

We have a gas-fired combi-boiler, therefore no hot water tank, therefore no immersion heater. I considered using a 15l unvented electric water heater I've got lying around to preheat the cold water feed to the boiler, but Worcester Bosch told me if I did that, I'd break it. However, they did tell me I could spend a fortune on one of their new models, which would accept a pre-heated feed. Er, no ta. Due to the way in which the power diverter devices work, they can only supply a resistive load, ie. a heating element like that found in the average immersion heater. Fortunately, this means they'll also work with electric panel and storage heaters (but only the basic 'no frills' ones without fans, timers or electronic controls). The plan is to therefore divert our excess pv generation into space heating. I've already sourced a snazzy, slimline 400W panel heater which I've installed on the landing and which should hopefully work in conjunction with our 'fresh air' positive input ventilation system, the outlet diffuser of which is located in the ceiling above the heater. I'm hoping for a mixture of pre-heating and destratification, as the two work together to waft gently warmed air around the house. Seems to sort of do something resembling that, following some initial trials.

Slimline 400W heater for 50 quid. Bargain.

 The main business will be taken care of by a couple of 1kW or so storage heaters located in the downstairs living areas. We're currently on the look-out for a couple of suitably cheap, used units to be added as and when. We hope they will be able to take a bit of demand off the gas central heating system.


That only leaves the power diverter device. I have installed quite a few Immersun units for customers with immersion heaters and this high quality, well thought out bit of kit works very well. However, it is far too sophisticated (and expensive!) for our needs. A bit of seasonal space heating will be nowhere near as cost-effective as year round hot water so a more basic alternative was required if this project was going to be worthwhile (not that we've bothered with such trivialities as working out the financial benefits!). The answer came in the shape of the Solamiser, a trimmed down controller with none of the Immersun's bells & whistles. More Aldi than Waitrose, if you will. Still, at a fraction of the cost of its flashier cousin, I am hoping it will perform as good a task. Hoping to get it fitted in the next week or so.

The Solamiser. I might buy a bell and a whistle to pimp it up a bit.