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Author Topic: Is solar thermal heating out of date ?  (Read 7814 times)

Rob Dekker

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Re: Is solar thermal heating out of date ?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.
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etienne

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Re: Is solar thermal heating out of date ?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

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Re: Is solar thermal heating out of date ?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

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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

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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. ;)
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Sleepy

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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.
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Sleepy

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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 »
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etienne

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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

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Re: Is solar thermal heating out of date ?
« Reply #58 on: May 01, 2018, 08:00:55 AM »
Very little.
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Sleepy

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Re: Is solar thermal heating out of date ?
« Reply #59 on: October 21, 2018, 12:01:15 PM »
Haven't updated on the Eddi & Harvi since April because there was a big issue for me and everyone else out there who's on 3-phase grids. Despite what the manual claims, there's no support for 3-phase systems and further; the feature to set an export margin doesn't work either. So I had to rewire some stuff at home, otherwise the Eddie would increase my electricity consumption...

The reason for updating now is that they (after close to five months of silence and ignoring emails about the timeframe) promises to roll out the firmware update. I'm looking forward to it. But the dark months are here now so I won't have any use of it, until spring.
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Sleepy

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Re: Is solar thermal heating out of date ?
« Reply #60 on: November 15, 2018, 08:59:22 AM »
Patience is a man's best friend, the update (including the required hub) should be on it's way now. Yawn.
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Sleepy

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Re: Is solar thermal heating out of date ?
« Reply #61 on: November 19, 2018, 09:32:35 PM »
Lifting this thread since it's close to my own issue now. I've retired my solar hot water panels after the latest recent failure and temporarily placed PV-panels on top of them (at a 51° angle which is spot on this time of year).

I've ordered this unit together with a "harvi": *ttp://myenergi.uk/products/#eddi
A bit expensive but specs looks good and if someone in here has any real world experience of it, I'm all ears.

What a lucky coincidence, today on November 19, I recieved the hub and should be able to update my Eddie so that it should be able to work properly on a three-phase grid. Adding the updated manual for the Eddie and also the update pdf's sent out for both the Eddie (available FW version 2.027) and the Zappi (available FW version 2.000).
The unfortunate part is that I've got at least two dark months ahead.
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etienne

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Re: Is solar thermal heating out of date ?
« Reply #62 on: November 19, 2018, 10:35:04 PM »
Last summer I contacted Myenergi to ask them about 3 phases car loader and they told me that it would come sometimes around the end of the year.
It sounds normal that the 3 phases Eddi would be available at a similar time.

Sleepy

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Re: Is solar thermal heating out of date ?
« Reply #63 on: November 19, 2018, 10:41:35 PM »
The problem is that they promised that in the manual. Along with other features not working, see up thread. Manual in #14 and also see my post #59.

Edit; What do you mean by "last summer" etienne? I was in contact with their tech guys in early May about these issues (and bugs) in the firmware.
« Last Edit: November 19, 2018, 10:58:02 PM by Sleepy »
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etienne

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Re: Is solar thermal heating out of date ?
« Reply #64 on: November 20, 2018, 05:33:52 AM »
In July or August this year because we work on a residential project with a parking lot for 12 cars, and the builder promised EV loader to the customers. The normal Zappi is very interesting in that context because it allows a very low intensity loading (6A on 1 phase, which means 24 cars if you have 50 A on 3 phases), but the problem is that it doesn't allow yet fast charging (here 32A on 3 phases) when only one car requires loading. Such a fast loading is not really needed, but it's difficult to explain that you decided not to offer that possibility. Standard 3 phases systems can only load on 3 phases, and 6 A seems to be the minimum required current, so this only allows the loading of 8 cars if you have 3 phases 50A.
Residential is complicated because people have private parking places, so everybody needs his own loader. Anyway, you can't ask people to stand up in the middle of the night to change loading configuration in the parking lot.

Sleepy

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Re: Is solar thermal heating out of date ?
« Reply #65 on: November 20, 2018, 07:09:43 AM »
I'm talking about real world issues and bugs in the firmware for the Eddi that I own, not Zappi, but both use Harvi to monitor three phases.
Only Harvi has three CT inputs for three-phase supplies. Eddi/Zappi only has two CT- inputs internally.
Clear enough?
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etienne

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Re: Is solar thermal heating out of date ?
« Reply #66 on: November 20, 2018, 07:32:44 PM »
I didn't know Eddi was a one phase heater. At work we use MYPV (http://www.my-pv.com/en/). It's a German product and Germany work with 3 phases just like Luxembourg, it makes things easier.

In Luxembourg, injection price is still higher than electricity costs, so I think that it doesn't make so much sense, I always compare it to a Ferrari, it's cool but it's much cheaper to drive a Twingo, and the final result is the same.
---
Addendum

My boss likes projects with minimal "imported electricity", I prefer the concept of minimal electricity consumption. He will overheat and store the heat, I would use the heat pump to minimize consumption and sale excessive production. If you look at the efficiency of a heat pump, price difference has to be very important to have direct electrical heating from PV cheaper that heat pump heating.

---
Second addendum

I still hope that excessive PV power would make projects like hydrogen production from renewable energy possible.
« Last Edit: November 20, 2018, 07:37:57 PM by etienne »

etienne

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Re: Is solar thermal heating out of date ?
« Reply #67 on: November 23, 2018, 11:06:58 AM »
I received an interesting link for small home PV configuration yesterday.
http://simon.energy/
Still expensive, but ok for a "just for fun" concept.