Support the Arctic Sea Ice Forum and Blog

Author Topic: Is solar thermal heating out of date ?  (Read 3509 times)

Rob Dekker

  • ASIF Upper Class
  • Posts: 1577
    • View Profile
  • Liked: 34
  • Likes Given: 30
Re: Is solar thermal heating out of date ?
« Reply #50 on: April 07, 2018, 09:35:22 PM »
Thanks, Sleepy.
It looks like the efficiency of thermal heating in that hybrid panel drops off as fast as a normal thermal heating panel that is 'unglazed'.
Here are efficiency numbers for a normal thermal heating panel :



Since PV efficiency also drops off with higher temperatures, it looks like this hybrid panel is kind of combining the worst of both systems.

It appears that you can get much better performance by creating two separate systems. One (hot one) for thermal heating and one (cool one) for PV.

etienne

  • ASIF Citizen
  • Posts: 370
    • View Profile
    • About energy
  • Liked: 7
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #51 on: April 07, 2018, 10:04:53 PM »
Thanks for the graph. It's very interesting.

This is a product for the European market, our roofs are much smaller than in the US. The applications I know about are on residential buildings, which means a lot of people for a small roof surface, which is why there is that heat pump application. The problem with heat pump is to have the smallest temperature difference between cold and warm side, so with 20°C cold water, you can get a better efficiency than with standard system when producing hot water.

If you want 20°C water, you don't really need to insulate your panel.

In Europe, there are also subsidies for using new concepts. This is a typical project that could apply.

etienne

  • ASIF Citizen
  • Posts: 370
    • View Profile
    • About energy
  • Liked: 7
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #52 on: April 08, 2018, 06:55:24 AM »
Another application for these panels is in combination with the Ice Storage from Viessmann.


If you can't do geothermy, you can use a big tank of water (serveral cubic meters, I saw a projet with 700 cubic meters) and take the heat out of it. As long as the whole tank is not frozen, ice temperature stays at freezing point, so you can get water at 0°C for your heat pump, which is much better than low depth (5 to 10 meters) geothermy.

To reduce the size of the ice storage, the tank can be heated using solar panels, so even in the winter, you can get some extra heat. Solar panels can also provide heat directly to the heat pump.

The tank is not insulated so that you get some extra heat from the ground.

If you check the values on the graph,
- heat coming in the ice storage + cooling going out = heat going to the heat pum.
- heat going to the heat pump < heat going out, and this is because of the electrical consumption that is transformed into heat.

During the summer, the ice can be used to cool the building. The difficult thing is to have enough ice for cooling in September, and no more ice in october when heating season starts.

This system is quite expensive.
« Last Edit: April 08, 2018, 07:07:49 AM by etienne »

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 19
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #53 on: April 08, 2018, 07:52:28 AM »
The PV+ice storage thing is neat. I see multiple AC applications for that. Thanx.

sidd

Sleepy

  • ASIF Middle Class
  • Posts: 931
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #54 on: April 09, 2018, 07:02:01 AM »
Been away for the weekend but that's my old dream that will never be. It doesn't have to be expensive if you are willing to do some heavy work yourself and has some knowledge about heat pumps.
Thermal storage tanks are nothing new. I have a slighty larger, and rather old, dream that I've never realized. :(

Heating during winter is the main problem in Scandinavia, even if winters are becoming warmer and warmer. So; bury a large sturdy tank that withstands freezing, feed it with solar hot water panels, then use a heat pump to warm the house. By doing so, I can use the panels more efficently at really low temperatures and also be able to utilize the phase changing properties of water. A heat pump filled with propane or propylene will be efficient in harnessing heat from zero degrees.

But with the winters lately I will do just fine with the three homebuilt and interconnected air to air/water systems I use now. The oldest of them is thirteen years old and it runs every day, all year around.

Thanks, Sleepy.
It looks like the efficiency of thermal heating in that hybrid panel drops off as fast as a normal thermal heating panel that is 'unglazed'.
...

Since PV efficiency also drops off with higher temperatures, it looks like this hybrid panel is kind of combining the worst of both systems.

It appears that you can get much better performance by creating two separate systems. One (hot one) for thermal heating and one (cool one) for PV.
Pretty much my own conclusion as well, Rob. There are certainly uses for this but not for everyone and it's a lot better than solar roadways. ;)
Omnia mirari, etiam tritissima.

Sleepy

  • ASIF Middle Class
  • Posts: 931
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #55 on: April 09, 2018, 09:47:48 AM »
One idea I've had is a glass box big enough for your house and an air cycle heat pump moving the heat from the glass box back into the house.
Consider the outdoor unit's air flow rate, my smallest and oldest (14yrs old now) can consume 2150 m³/h which equals 51.600 m³ of air per day. Also consider that water (vapo(u)r) carries the energy. Your box will quickly become very dry, cold and inefficient for a heat exchanger, in heat mode the outdoor unit is the evaporator, so you would need to figure out how to re-humidify the air as well.
A super sized glass box, would be frozen solid at my latitude during winter and colder/drier than the ambient air and therefore rendered useless.
Omnia mirari, etiam tritissima.

Sleepy

  • ASIF Middle Class
  • Posts: 931
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #56 on: April 30, 2018, 07:29:11 AM »
Got my Eddi & Harvi on Friday the 27th, installed it Saturday. Manufacturing date on the attached sticker; 23/04/18. Docs posted here:
https://forum.arctic-sea-ice.net/index.php/topic,2061.msg146501.html#msg146501
I also had clouds of course, and forecasts with even more cloudy days... That seems to be a standard feature of any solar and wind installation.

There were some openings in the cloud cover, so I managed to get a couple of short videos. One from the main screen and one from the Harvi CT screen. The speed of the Eddi was one of the most important considerations I had beforehand. Not much energy sent to the grid and it adjusts really fast to shifting loads. Nice!

Now I'll be waiting for a clear sunny day, then I'll decide what to do with my hot water panels. Repair or remove.  :-\

Edit; removed the second video.
« Last Edit: April 30, 2018, 09:36:19 AM by Sleepy »
Omnia mirari, etiam tritissima.

etienne

  • ASIF Citizen
  • Posts: 370
    • View Profile
    • About energy
  • Liked: 7
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #57 on: April 30, 2018, 07:18:25 PM »
Looks a little bit like the SMA interface.

Sleepy

  • ASIF Middle Class
  • Posts: 931
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: Is solar thermal heating out of date ?
« Reply #58 on: May 01, 2018, 08:00:55 AM »
Very little.
Omnia mirari, etiam tritissima.