First steps to using solar energy

Solar? Saving on energy consumption in the home? Are you serious?

Well yes I am.

I have for several years looked at the various merits of solar panels. (Ground-source and air-source heat pumps are another subject for another time)

By now I reckon I have a pretty good appreciation of the subject. (I may look back on this blog and realise I was wrong)

I have investigated water heating panels (flat plate, or vacuum tube), PV panels generating electricity, and air heating panels (most of these seemed to have a ‘home-made’ feel about them, in the USA some types are made with old soft-drink cans!)

I enjoy reading the technical stuff like average UK daily “insolation” (sun’s energy) each month of the year, I find this fascinating. And energy conversion ratings such as watts (w) energy output per hour in overcast, bright or very sunny conditions are published by some vendors. This gives you an ability to compare raw numbers for different units. I shall come on to some of the details in a minute.

The issue for me came down to initial investment cost, and complexity.

I wanted to produce some heat in the house from the sun. I knew it was possible. But which solution should we choose?

Some of my findings.

PV solar panels, generate very little energy for each M2 (square metre) of panel. OK it’s easy to carry the energy inside the house, because it’s electricity that it generates, but the best on the UK market are still only 16% efficient. And I was expecting to pay £500 for a 200w (max. rating) electric panel.
That’s before installation, where an inverter is required (£600) to convert 12v (Volts) to 240v. (Grid tie inverter, plug the output into a socket, and voila, electricity straight to the rest of the house)
The panels have to be big to achieve this 200w output.
Around 1000 watts of energy are present during regular sunshine for each 1M2 of UK land surface. Therefore 16% efficiency means the panel must be 1M2 to generate 160w of energy.

Water heating panels (vacuum tube especially) are efficient at capturing the sun’s energy, but you need all the water pipes, pumps, non-return valves, pressure release valves (for July sunshine) and a radiator within the property on a closed loop.

You can of course use the energy to heat your tap water. But the hot water bill in summer for us is about £18, (our summer quarter bill is always very low) and the system plus install would be about £2000 for tap water heating.

So I thought perhaps air heating was my best option. It seemed less complex, less parts, easier to install and therefore slightly less expensive. The guide price for the large unit “SV14” we were considering on the http://www.solarventi.co.uk/ web site was around £900 plus vat, plus install. It was claimed that up to 600w energy could be produced. The unit is 2M x 0.7M, i.e. approx. 1.4M2.

Simply, the Solarventi models aim to heat out-side air and push it into the building thus contributing to a recycling of air that is in the house. Stale air inside the house is pushed it out through those cracks and crevices around windows, doors etc.
It is rated highly any time of year, but particularly on those winter days when the sun is low, the ground is frosty, and the out-side air is very dry (low humidity).

Why is that important? Well, low humidity air in winter, can, it is claimed, in effect dry your house. Moisture takes plenty of energy to heat. So, unless you have a grand-piano with a requirement for moisture, it’s a good idea. We are hoping that in winter moisture around the inside of windows will also reduce over time.
The Solarventi solar panel is installed out-side on a wall or roof. It sucks out-side air into the unit, warms it and a PV panel generates a small amount of electricity to drive a fan to impel the air into the house.
Our unit only seems to work in bright sunshine. But that’s the idea I guess, bright winter sun equals dry, crisp air outside. Over the months we should see a warming of the house, and a drying too.

So where did we install the Solarventi unit? It’s on the external wall outside the bathroom, facing south, of course. Ideal we hope for capturing low winter sun.
We had a choice where the vent into the house should be piped, through the roof space, from the unit. But we chose the solarventi to vent into our bathroom.
At least it will when we next have a bright sunny day. Wed. the day of the install was bright and sunny, and the unit worked fine as we inspected it before it was lifted in place onto the wall. It has been overcast since then.

I have a couple of photos of the install, and over time I will report on the results. The installers kindly helped me install a hygrometer, (humidity gauge) which has a remote temperature sensor. They placed the sensor on our outside wall next to the solar panel. So I have been taking daily readings of inside temp, inside humidity, outside temp. and recording the amount of bright sunshine.

The challenge then for this solarventi unit is, over time, to reduce the humidity (and unsightly mould) in the bathroom in particular and we are told to expect the other rooms upstairs to benefit also.

We shall see.

Installation

Wed. 21st Jan 2009.



Thank you Jesus, it is a dry bright day for installation. (You are a bit too exposed installing a 2 metre solar panel on a south facing wall for it to be raining or snowing!!)




The staff from Solarventi were booked to perform the installation. Good communication prior to the day regarding the layout (inside and out), suggested to me the install would be successful. I was pleased with the communication on the day; discussion and explanation of the approach to the work made me feel well informed.




The gadget just before it is raised up the scaffold.




Aluminium backed unit has many tiny perforations to allow air into the unit to be warmed and vented into the property. The vent output is pictured at the top next to the regulator cable. The cable was fed into the house to a rudimentary thermostat / control unit placed on the upstairs landing.

It should give adequate control over the panel output.



December and January have been cold and dry for the most part. The forecast is for rain for the rest of the month.
Hmmm...