Hello - solar electric expert here - DIY Chatroom

mboxwell · 07-01-2009, 12:52 PM

Hi. My name is Mike and I'm new to the forums.

My background and specialist area is solar photovoltaics, having done a number of projects on them (and writing a book on them as well).

If anyone has any ideas for a solar project, or any questions about them, just ask and I'll do my best to answer them!

I'm not connected to any particular supplier of solar hardware so I am vendor independent. Mind you, I might threaten to sell a copy of my book

Past projects have included building my own house and restoring a couple of classic cars. Current projects are a bit more mundane - refitting the kitchen and grouting tiles in the bathroom

I'll get round to finishing them someday...

Knucklez · 07-01-2009, 03:40 PM

hi mboxwell,

some time ago i designed a line interactive photovoltaic inverter. i synchronized it to the grid and - for a brief moment - delivered power to the utility & see the meter go in reverse. did this as a school project. then i found out later that it requires an independent power producers license.. and so ended said project. but it was fun while it lasted. i always wanted to get back into it.

here is an idea i had about a solar project...
i live in a cold climate, northern hemisphere. i wanted to make a solar hot water heater similar to this project HERE. then i want to run some tubes in concrete (pex?) when i pour the cement for my driveway. then i want the solar hot water heater to heat the water which warms the concrete drive way which melts the snow. and i don't have to shovel anymore.

what do you think? think i can generate enough warm water to do this in a reasonable residential DIY project sort of way?

Knucklez

mboxwell · 07-01-2009, 05:45 PM

Sounds an interesting project. Similar things have been done here in the UK, although I don't know much about them. The problem is you don't get a lot of solar energy during the winter when you most need it.

You might find a DIY ground source heat pump would be more effective though, if you've got the space to build one. This would bring up heat from underground to help heat up the driveway.

The problem you will have is the large surface area of the driveway, which means that it would be difficult to keep warm.

**AtlanticWBConst.** · 07-02-2009, 09:55 AM

Hello Mike,

Welcome to the site.

Yoyizit · 07-02-2009, 01:00 PM

Quote:

Originally Posted by Knucklez

i live in a cold climate, northern hemisphere.
generate enough warm water to do this in a reasonable residential DIY project sort of way?

Will 3.3 kilowatt-hours per square meter per day, average, for Ontario, do it?

mboxwell · 07-02-2009, 02:45 PM

That is the average over a period of a year, not in the winter!

I've checked the insolation figures for Toronto and this is what it looks like over a period of a year:

January 1.38kW/h per square meter per day
February 2.23kW/h per square meter per day
March 3.30
April 4.55
May 5.50
June 6.04
July 6.02
August 5.22
September 4.07
October 2.67
November 1.60
December 1.18

Those figures aren't bad to be honest - I wish the UK was as good. That said, my gut feeling is that it is not going to be enough. Or if it is, you would need a very big solar collector to generate enough heat in winter to keep the driveway snow-free.

mboxwell · 07-02-2009, 02:48 PM

Actually, I think I know how to do it - how to keep the snow cleared off your driveway in winter using a solar panel.

Here's what to do:

Build a small solar water heating panel and prop it up outside the front of your house in view of the road.

After a while, you'll start getting curious and interested glances from different people. Sooner or later, somebody is going to ask you about it.

Explain to them that it is a solar water heater and that it can provide free hot water using the power of the sun. If they seem interested, tell them that they can have it for free, if in return they agree to sweep the snow off your drive during the winter.

Bingo - you've built a solar hot water panel and your drive stays snow free all winter.

Yoyizit · 07-02-2009, 04:38 PM

Quote:

Originally Posted by mboxwell

I wish the UK was as good

One day while driving my rental car around Portsmouth the radio announced that it would be extremely warm today-75F!

Snowfall in the UK: a dog became an annoying beer drunk and
it snows every 10 years in Cowplain.
So the dog woke up to a snow-covered landscape one morning after a drinking binge and
gave up drinking.

Bottomdweller · 07-03-2009, 01:37 AM

Welcome Mike, I'm a newbee myself. I'm a little confused. I have a small sailboat and I resently installed a small solar panel. I think it produces 4 watts at peak. I have the panel mounted on the top of the bimini and I know this is only a trickle charge from my batteries, but when it rains and the water puddles on the panel, my watt meter flucuates. According to the meter, almost a whole watt. Is the water causing some type of magnafication effect or have I just had to much to drink?

Thanx and welcome again
Bottomdweller

mboxwell · 07-03-2009, 10:43 AM

Quote:

Originally Posted by Bottomdweller

Welcome Mike, I'm a newbee myself. I'm a little confused. I have a small sailboat and I resently installed a small solar panel. I think it produces 4 watts at peak. I have the panel mounted on the top of the bimini and I know this is only a trickle charge from my batteries, but when it rains and the water puddles on the panel, my watt meter flucuates. According to the meter, almost a whole watt. Is the water causing some type of magnafication effect or have I just had to much to drink?

Thanx and welcome again
Bottomdweller

Are you saying that the power increases when you have water on the panel, or reduces? If it is increasing, I can only think that there is some sort of light concentrator effect going on.

Yoyizit · 07-03-2009, 01:47 PM

Quote:

Originally Posted by mboxwell

Are you saying that the power increases when you have water on the panel, or reduces? If it is increasing, I can only think that there is some sort of light concentrator effect going on.

Sure. Water droplets with a convex surface can only cause magnification of the sun's rays.

mboxwell · 07-04-2009, 03:17 PM

Quote:

Originally Posted by Yoyizit

Sure. Water droplets with a convex surface can only cause magnification of the sun's rays.

Magnification? Or concentration? I can understand a small magnification effect, but a convex surface is going to concentrate the light to a smaller point on the surface of the panel, and the effect of that should be minimal in terms of electricity generation. In hot weather this could actually damage the panel over a long period of time.

I've been doing some experiments here with an old amorphous panel and I am not getting any discernable improvement by adding droplets or puddles of water onto the array. In fact, with a puddle of water I'm getting about a 10% decrease in power generation, which is what I would expect.

Yoyizit · 07-04-2009, 04:04 PM

Quote:

Originally Posted by mboxwell

Magnification? Or concentration? I can understand a small magnification effect, but a convex surface is going to concentrate the light to a smaller point on the surface of the panel, and the effect of that should be minimal in terms of electricity generation. In hot weather this could actually damage the panel over a long period of time.

I've been doing some experiments here with an old amorphous panel and I am not getting any discernable improvement by adding droplets or puddles of water onto the array. In fact, with a puddle of water I'm getting about a 10% decrease in power generation, which is what I would expect.

I stand corrected; the panels that use convex lenses use lenses big enough to cover the whole panel with light.

Doesn't all the light get through the water?

mboxwell · 07-04-2009, 05:42 PM

Not all the light will get through water although the vast majority will.

Some of the light will refract off the water (which is why droplets glisten and sparkle in sunlight), and some of the light will be absorbed by the water, generating heat and eventually evaporating the water off the panel.

Bottomdweller · 07-18-2009, 06:45 AM

Quote:

Originally Posted by mboxwell

Are you saying that the power increases when you have water on the panel, or reduces? If it is increasing, I can only think that there is some sort of light concentrator effect going on.

Yes sir, it increases and the effect you have discriped sounds like what is going on. Is this common or have i discovered something? LOL