Doesn't know what they are taking about!

[DamonHD]

Hi,

I'm taking my solar DHW project a little more seriously now, and I believe that I am approaching sanity from one side or the other in my plans (no more buried milk tankers for me any more, oh no, I'm off the milk wagons B^> )!

So I've started asking for quotes, using my friend Google to help find potential suppliers.

What I did was write up my aims and outline spec:

http://www.earth.org.uk/note-on-solar-DHW-for-16WW.html

and send a short email asking the supplier to give me a rough price against the 'Basic' spec and/or tell me what other information might be needed, get in contact, etc...

Ah well, just now I received an email starting:

The person who wrote the article doesn't know what they are talking about and the possibility of 100% by solar as they imply is something they will never achieve.

I understand that they didn't check the copyright line at the end to see it was by me, but ummm.

And I believe that some of you might have something to say about 'never' achieving 100% solar DHW (depending on whether 95% or 98% or 99% or 99.6% might be considered near enough).

Anyway, I'd hoped that I was being clear in my page that I was really only hoping with the basic system to displace gas DHW heating more or less entirely March--September (ish).  Is there any obvious simple thing that I could add/change to be clearer?

(I've not dumped the response mentioned above, but I have let the guy know that it's my piece...)

Rgds

Damon

[DamonHD]

(To be fair to my brusque correspondent, I have just edited the text a little and emphasised 'may' be able to get year-round DHW.)

[Stonebrain]

Hi Damon,

I didn't do it myself(yet), as you know the best sailors are on the quay.

The crucial thing is orientation and inclination of your collectors.

The west orientation might be acceptable for summer but will be bad for the winter.(depends on the inclination too)

Placing the collector on the part of the roof facing west doesn't mean you have to orientate it west.You still can orientate it south.Maybe this can hurt aestethic feelings,but aestetics is very subjectif.

You have to fix the two 'south'-corners of your panel on the roof and lift the two 'north'-corners until the orientation is good enough.

If you do it this way,you can not achief any inclination you want plain south as you could do in case your roof is facing south,due to geometrical constraints,but you can improve greatly the winter- and overall performance.

As a rough rule you can consider 45°inclination plain south as optimal for year round yield(this may vary some with the geografic situation).

But in case you have too much dhw in summer you can put the panels to a more vertical inclination,this may lower the year-round and summer yield but can improve the winter-yield and in consequence cover somewhat better your needs.

Someone posted a link some time agoo to a site where you could find the daily yields for any orientation and any inclination for any day of the year on any place,a great site for solar dhw-guys but I lost the link and cannot find it back again.

I hope someone can find it for us.

Some guys on this board can find any link.

Please help us!

cheers,

Jaap

[disaray1]

 Damon,

  100% coverage is more than any retailer will promise. Even in the "Sunshine State" Florida...the solar dudes wont even think of making that 100% claim. Too many variables. 3 or 4 days of continuous overcast skys will bring even a properly sized system to it's knees- and believe me- your wife WILL let you know about it. At your latitude and with the collector(s) facing other than south, I'd guess you'd be fortunate to see even 75%.

 My experience is with flat plate collector, evac tube is supposedly more efficient, and obviously more expensive.

 Also, when I purchased the system that we use now (32 sq ft collector facing south, 80 gal tank), not a single solar store here would install anything but a electric backup tank. We were using a gas water heater, and I wanted gas back up, but of the four companies that I contacted, none would do that- something about the big hole in the middle of the tank losing all of the heat thats been gained. Maybe things are different now?

 May the warmth be with you.

 David

 BTW- I had to fire up the electrics for DHW 4 times this past winter, and always because of mutiple cloudy days in a row. Definately not 100%, unless you can stand 55F showers...

[scottsAI]

DamonHD,

Yep, not 100%. Even in, as mentioned in Florida to hit 100% need days of storage, making the system not cost effective. Making it 100% when the sun shines is all together possible!

Since you have a west and east roof then the end of the house is facing SOUTH!

Vertical collectors work well in the winter! Put on south end of house.

Over the windows put collectors like an awning...

Have fun,

Scott.

[DamonHD]

Hi,

A agree entirely with you in principle, which is why I left the north end of my west-facing roof free.

But the planning authorities have made it fairly clear that they won't approve anything that isn't parallel to the roof line.

In a way, tube collectors do present quite a decent profile sideways, and are otherwise good for winter performance, but beyond that I am resigned to live with an extra-large drop in winter.

All the incident energy info for the EU (and Africa) is available at the PVGIS site:

http://sunbird.jrc.it/pvgis/

Although it claims to be for PV, the raw underlying insolation numbers are just as easy to get at.

Rgds

Damon

[DamonHD]

Nah, the south end of the house is my neighbour's interior bedroom wall (we are the end of a terrace)!

I have a complete north-facing exterior wall, but no south-facing exterior wall at all.

Rgds

Damon

[Gary D]

 Damon, what you are trying to do is admirable. In some countries they are using a wax (paraffine I think) as a storage medium. I haven't searched anything about it, but the phase change is the key, so I'm told. It supposedly can store 8 to 10 times the btu's per size unit than water. Perhaps if you have time and desire, it may be worth your while checking out? This could be an auxillary backup for when your preheat is up to temp. A spare helper for sunless days? Sorry for the poor speling...

[Stonebrain]

Thanks for the link.

Not exactly the one I meant,but usefull.

I put it in my bookmarks

cheers,

Jaap

[DamonHD]

I think that it's pretty tough to beat water as a (non-toxic) storage medium at reasonable temperatures by the $ and the kg, but I'll definitely have a look, thanks!

Rgds

Damon

[DamonHD]

Well, the bloke called me and spoke to me today: he was fine to talk to and he'll come over and make a survey in person early next month.

Rgds

Damon