Solar Radiation and Latitude

[MountainDon]

This is sort of connected to building and then again, maybe not. Glenn?

Common sense and Science indicates that the further north on goes the less intense the sunlight, the solar radiation.

I've been tracking the amount of solar radiation here near home and up in the mountains near my cabin site. The mountain site is less than 50 miles north of home and 3500 feet higher in elevation. I'm using data reported by two remote sensing/reporting weather stations. The solar radiation is reported in watts per square meter. It is reported at hourly intervals, the mountains at 8 minutes after the hour and the close to home site at 42 minutes past the hour.

Except for days when the cloud cover is obviously quite different a pattern has emerged. Comparing the maximum reading from each station the mountains are consistently 2 to 3 % lower.

I found it interesting; YMMV. 

[ScottA]

Also the further north you go in winter the shorter the day is.

[MountainDon]

Also the further north you go in winter the shorter the day is.

Yes. Another change between summer and winter is (comparing where I was born, Canada, to where I am now NM) is...
summer: the sun rises earlier in the north and sets later in the north giving a longer summers days. Very nice. The short daylight hours are a bummer in winter though. As much as 100 minutes difference in sun time.

Sunrise/sunset links:
http://www.sunrisesunset.com/
http://www.sunrisesunset.com/custom_srss_calendar.asp

[mvk]

Don
I have a ton of books from the 70's that have solar insolation charts, have you done any comparisons between now and then, might be interesting with all the climate change stuff?

I pretty interested in anything you say, loved the post on tires, any chance you could do one on batteries. I need to get one for my car and if I'm honest with my self I know nothing about them even after buying them for 40+ years.

Now I hijack the thread. Passive Solar? I searched this site for that, solar green houses, and sun spaces not much here. John sells his solar kit and greenhouse/sun space stuff. I study this back in the 70's attended a lot of work shops and such and took some courses. Toured all the local projects and helped build some. What I walked away with was that it doesn't take much south facing windows to over heat a well insulated house, that a lot of south glass is hard to live with and really cold at night or when it's cloudy, that a solar greenhouse can heat your house or grow food but can't do both very well, that night time insulating glass was hard to do well and expensive and that storing the heat and redistributing it was hard to do well and expensive. Used to think that Steve Baer's idea to blow insulation between glass was a perfect solution anyone know if that got perfected. Whatever happened to phase changing salts?

Anyone else thinking or working with this?

Mike

[ScottA]

I think the trick to passive solar is lots of thermal mass to store the heat gained during the day and help prevent overheating. Getting the balance right between glass and mass could be tricky though. Also the mass needs to be insulated from the ground and the outside air. With enough stored energy the heat loss from the glass wouldn't be such a big deal.

[John Raabe]

Thermal mass is where a passive solar home stores heat, but to work best it needs to be balanced with the climate. You can certainly have too much of a good thing.

In an ideal solar climate such as New Mexico, you have sunlight almost every winter day and the thermal mass can be recharged from the night's losses. Thermal storage acts like an energy flywheel making the exchange within the comfort range of the house.

In more northern cloudy climates, such as coastal Washington state, you may not see the sun for five days. This often cools the mass down to the point that a days sunlight will not be able to bring it into the comfort range of the house.

My sunroom is a prime example. It is an unheated space with an insulated concrete mass floor and lots of south facing glass. It contributes usable heat to the house in the Spring and Fall when we open the doors and windows between the house and sunroom on warm days. It allows me to have a heating season that is perhaps 8 or 9 weeks shorter than my non-solar neighbors. This is good!

But today the sun came out - it was cold last night (26ºF), and it has been sunny all day for the first time in a week. The sunroom temp at 2 pm is now 54º. It will get no higher today. That is far above freezing but we are not going to open the 69º wood-stove heated interior and use that heat today. With less mass it might have gotten to 70º or more out there.

So, for maximum use of sporadic solar heat such as this you do not want to have a lot of thermal mass getting in the way. I would be better off in a direct gain situation where the south facing windows were not in the sunroom but in the house itself. Then the heat would come directly into the living spaces.

Of course all that extra solar glazing would also have been losing heat for the last week of cloudy weather.

My point is that more thermal mass is not necessarily a good thing. It needs to be balanced to the climate pattern.

For more see my booklet called the Sunkit where I try to give guidelines for workable inexpensive passive solar.

http://www.countryplans.com/solarkit.htm

[MountainDon]

Don... ...any chance you could do one on batteries. I need to get one for my car and if I'm honest with my self I know nothing about them even after buying them for 40+ years.

Now I hijack the thread. Passive Solar?

BATTERIES, automotive... go HERE for my biased opinions 

As for passive solar... I looked at it way back in the 70's too. When we moved to NM in the early-mid 80's we made limited use of the then current solar technology. We have a couple old air exchange panels that do supply a good amount of heat during our sunny days. But we do not have enough thermal mass to take full advantage of it. Retro-fitting seems like too much expense/bother.

I think John said it best. It depends. Except he didn't come right out and use the "D" word. 

[John Raabe]

Depends is right!

To get past "depends" I always try to Sell something!

Isn't that the American Way?

[mvk]

Nothing wrong with trying to sell something john but the sun kit might be a tough sell to me I think I did most of that 25 years ago for my land. Any good new ideas for night time window insulation? And what ever happened with those salts everybody was going on and on about them. Cold fusion? I will probably over glaze mostly on the south side but also on the east. I'm a morning person and love south east light and sun and it really just works on my land. I'm having trouble coming up with a design because I want so much of the house with southeast windows bedroom kitchen dinning. Be nice to stop some of the heat lose and also store some of the heat gain if I'm going to get it any way. I might pay for some real good ideas for that.

I thought that when I first clicked on that link you posted there was something about a passive solar forum which I clicked and got a message that said I couldn't open it? I went around other things and then left meaning to ask you about it and when I opened the link I couldn't find it. I thought it might be a forum you needed to join plan help for? Did I just imagine that?
Mike

[MountainDon]

Any good new ideas for night time window insulation?

These are not new, we've had a bunch since 1985, all the way up to 8 foot wide. We think they are great. Easy operating, and they've lasted well. They're also good in the summer daytime heat. Some are room darkening (mylar film in between layers, and some let some light through.

[glenn kangiser]

One of our members has a great free solar site with tons of info -- here's a link to Gary's site.  http://www.builditsolar.com/

Check out the Trombe wall info. Interesting but not a window.  http://www.builditsolar.com/Projects/SpaceHeating/SolarWall/SolarWall.htm

[John Raabe]

Insulating covers are a great idea in almost any climate. Very practical and good return on investment.

For northern climates the trombe wall (in my experience) blocks too much light and often never gets up to temperature in the winter. I don't know of anyone doing phase change salts anymore. The ones I worked with in the 1980's were a bit like rechargeable batteries - there is an expectation of thousands of recharge cycles and then they seem to peter out in about 75 cycles or less.

My Sunkit booklet is now a free download for members of the PlanHelp subscription site. It is one of many downloads and if it is the only one you are interested in then it may not be worth the $29 three month subscription.

Here are direct links to the PlanHelp download pages:

Site tools  including the Sunkit.
Plan Details for updates to construction plans.
Template Plans for loading into 3D Home Architect ver. 3 or BH&G Home Designer.
Historic Plans like the bolt together vacation house.
Misc. Plans including the Sunroom and Skylight plans (also available here at CountryPlans.com)