I’ve just seen an advert for “Midnight Sun” in the daily mail. This is from a company called AWE – nothing to do with AWE Aldermaston which makes nuclear weapons.
Along with solar panels and the rest of the eco type stuff, they are marketing a gizmo called Midnight Sun which supposedly stores energy generated through the day for use during the night, thus saving you money ! Ostensibly a good idea but what is it.
Well, it can only be a battery, a battery charger and an inverter, hopefully a bit more electronics to synchronize with the phase of any solar panel inverter (Otherwise you are simply charging from the mains) .
Further research says about 9kWh of storage and 5kWh available (think 9 and 5 units of electricity ) So in simple terms a deep cycle battery, on ebay look for deep cycle gel battery 12volt 170ah which equates to about 8.5kWh and is about £250. Battery chargers aren’t expensive and inverters much the same, lets say £100 each for the top of the range, maybe £600 worth of kit including something to balance the phases. The deep cycle battery has maybe 700 cycles before it needs replacing.
This £600 worth of equipment will potentially store 5kWh of unused solar energy, assuming that over the day there is any unused solar energy and that the sun is out, so it might work at near capacity during the summer , hardly at all during the winter.
So we might save at max 5 units of electricity, lets say an average of 3 units a night -I’m being very generous! Each unit represents maybe 6p taking into account the savings in not buying it and the loss in not exporting it. Our £600 investment saves us at best about 20p a night or maybe £60 a year! So, ignoring battery replacement and any “money” cost associated with having £600 invested in batteries and not invested in savings, even at 1%, we have at minimum a 10 year payback.
Now have a look at their website : http://www.aweenergy.com/midnight_sun.php.
I was drawn to this by the full page advert in the daily mail for “Midnight Sun” / “Solar PV Payback Scheme” It sounds good, no mention of batteries, lots of “Solar Energy” , “Stored energy” etc. No mention of price nor actual savings.
Now read this: http://www.navitron.org.uk/forum/index.php?PHPSESSID=c24b607093cc3df8638529bcb5fefcbb&topic=18595.15 and we get an idea of the price, not £600, not £1,000 which might allow a bit of profit.
No, to get a price, apparently (according to the Navitron subscribers) you have to have the salesman visit, salesman usually equals a lot of commission . Well, the prices I have come across are from £5,500 upwards.
So, with a saving of £60 a year and that assumes the system really stores ONLY excess solar power! That means over 100 years to recoup your investment, but the batteries won’t last that long, maybe 5 years?
I suppose as a UPS / Battery backup it might work, but UPS’s are in the region of £100 not £1,000s