Question on covering solar collectors?

[alpcool]

Of course, these systems are very expensive, but have become much cheaper in recent years + with the ionic liquids, the production costs are reduced even further.
If a sufficient number is ordered then the prices are higher.
Without strong subsidies here (tax relief, for example) or political increases in the price of electricity (which is what we like to have here), such systems are not interesting.if you don't have your own proper manufacturers, then import them from abroad. I also have an import machine from Germany + cooler from italy.





first of all what maintenance costs? I have no maintenance costs. Absorption refrigeration systems are very primitive.

coefficient of performance is somthin of the 90s or 2000`s. We do use since 200er energy efficiency ratio (EER).
EAW in 98630 Römhild for example in Germany "Li-Br." starting 15 KW ( Prior 5KW) and is selling in projects in Switzerland. Lets stay stay in outdated unity "COP" 0,75. Starting at 172,4 F°Normal
"COP" for manufacturers at our market + CE at the moment is between 0,7 - 0,83 (Manufacturer Entropie for his very mig unites for example 0,83) on Li-Br. Most prototypes with ionic liquids are between 0.8 and 0.85 " COP" starting between 68° C and 78° C and will start the next 2-5 years.

I am amazed at the efficiency of "typical" solar collectors in your market of "typical" 65%. Mybe in US you do use another word for "efficiency" ? My collectors from 1999 do have 70% here.
Optical efficiency: The maximum solar thermal efficiency is achieved when the solar power absorber is at the same temperature as the surroundings. However, 100% efficiency is impossible.
The efficiency of solar thermal energy usually drops / warmer the absorber is in comparison to the surroundings. With regard to this phenomenon, one speaks of “optical efficiency”. The average solar efficiency here is between 70 and 85 percent. Manufacturers report the values of the optical efficiency for their products, which enables the efficiency of the technical systems to be compared in order to find the optimal solar thermal product. Chinese do it here too.


In summary, your calculations do not work with our manufacturers and conditions. It looks like you do have completely outdated technology + no suppliers etc.. I recommend an absorption chiller from Germany EWA for example to everyone here in my Canton who owns an normal house + normal payed tax payer job and if he produces enough excess heat energy in the summer ( a lot of sollar collectors).
This has the advantage that you do not need the ugly "usual" air conditioning systems made in china, you save electricity and money, as well as noise and can at least strongly reduce your income tax burden here. You also protect the environment from unnecessary power plant systems + the escape of climate-damaging gases + does not have to cover solar panels in summer.

[peakbagger]

Its always interesting how different parts of the world and regions have different approaches to heating and cooling. Evaporative coolers are popular in the western US due to drier climate while they are non existent in the eastern US where relative humidity tends to be high during hot weather. Local incentives also factor in. I looked for some of the manufacturers you mentioned and didnt find any US distributors. Generally manufacturers follow the money and sell products where they can make money, if they dont, distributors move in. In this case of absorption chillers in the US neither seems to have happened. Therefore its an opportunity for someone to make their next fortune or far more likely that the economics do not work out.

I will keep an eye out for these smaller capacity units and if and when they become commercially available in the US then its worth considering them in some areas.where the climate lines ups with their benefits. .

[bcroe]

Its always interesting how different parts of the world and regions have different approaches to heating and cooling. Evaporative coolers are popular in the western US due to drier climate while they are non existent in the eastern US where relative humidity tends to be high during hot weather.

Yes every area has different needs. Here it seems most advertisements are for
the oldest, noisiest, least efficient technology, but some change is appearing.

Here as we today have quite high temps and high humidity, my mini splits are at peak
efficiency, while being so quiet it is hard to tell when they are even running. Being able
to heat and cool, I have no need to supplement with gas heat some parts of the year.
Not even being connected to the gas line saves me not only the energy charges, but
the very expensive minimum connection fees that keep rising. The electricity comes
from my PV panels, which do not need to be close (and are 200 meters away).

The energy systems here have no effect on my income taxes beyond the installation
year. Bruce Roe

[LucMan]

Solar thermal has become obsolete with the current price of PV panels, heat pump water heaters, and Hyper Heat heat pumps and mini splits. PV is maintenance free, no danger of overheating or freezing, no pump failures, no possibility of leaks and the best part of all is the availability of net metering.
There is also the option of using air to water heat pumps if radiant heating, and cooling is desired. Solar thermal is no longer a viable option.

[J.P.M.]

Solar thermal has become obsolete with the current price of PV panels, heat pump water heaters, and Hyper Heat heat pumps and mini splits. PV is maintenance free, no danger of overheating or freezing, no pump failures, no possibility of leaks and the best part of all is the availability of net metering.
There is also the option of using air to water heat pumps if radiant heating, and cooling is desired. Solar thermal is no longer a viable option.

All that is probably 110 % true for most applications, at least in most of the developed world.

But the OP seems to be looking for thoughts on ways to avoid overheating with respect to an existing and apparently serviceable solar thermal (space heating ? or perhaps seasonal ?) system.

[LucMan]

All that is probably 110 % true for most applications, at least in most of the developed world.

But the OP seems to be looking for thoughts on ways to avoid overheating with respect to an existing and apparently serviceable solar thermal (space heating ? or perhaps seasonal ?) system.

The best answer I can give to that is to convert to a drain back system, remove the glycol fill with plain water, end of problem.

[Captron]

OK, Back to the original OP’s quest: Overheating.

There are so many crazy claims and counter claims about ST that I find it hard to talk to people that already have their minds made up. Here is reality for 2020.

To be clear I am in the business of Solar Thermal and have been for almost 2 decades. We have a new system preferably for new buildings that uses interseasonal storage. We can store MWt in this area and its huge, so this is the best way to prevent overheating, hands down, and it extends the solar heating into dark times and winter.

Retrofitting in low caloric heating systems (ie radian heat) is possible. If you have an existing hydronic heating system, and enough room adjacent, the storage system can be installed there and integrated.

No moving on to solar collectors (not panels) for hot water that overheats. Yes you Can cover the collectors, but it inhibits their performance on poor days of insolation. So how do you keep them cool?
The easiest solution is to divert fluid when it reaches sub 100C let’s say 93C (200F) and run it through a cooler like a baseboard pipe with fins behind the header box on EvT collectors or anywhere behind flat plate, or run to a pool or some other heat dissipating location. Then you can walk away and not worry about overheating. There are several ways to do this, so I won’t go into them here.

Efficiency: An EvT collector typically exceeds 80c efficiency. A PV panel rarely exceeds 20% efficiency.

EvT vs Flat Plate: In cold areas EvT collectors are the option of choice, they even run fairly well even at -30c, so for heating and even hot water they rule. In locations where winters are rarely colder than say -6c (20f), there a new flat plate collectors that will do, if less costly. In really warm winter locations it doesn’t matter.

EvT issues: If your solar EvT tubes are older than 5 years old there can be design issues for some EVT units. There are 3 main types of EvT’s:
Basic Heat Pipe collectors, the typical heat pipe installation: Typically double wall glass with vacuum between and no vacuum in the center. Older collectors had issues with cold weather. The interior of the heat pipe is a narrow heat absorbing pipe typically copper, where a moderate high vacuum is pulled and a water fluid injected. The new fluids have a copper content to stop them freezing up and warping the pipe. They work even in very cold weather. Heat pipe EvT’s are great for Drainback systems as the header allows the Drainback. If you have old Heat Pipes, the good news is you can USUALLY replace them, fairly inexpensively.
High temp heat pipes: These operate as above but are sealed through the glass, usually single glass with vacuum inside. Not recommended for residential use.
U tube EvT’s: Less common but These are the most efficient, often as high as 90%, but lack any control of heating except by increasing heat transfer fluid flow. They don’t drainback due to the network of headers and pipes. Only the glass double envelope can slide off during service.

So there is a primer on these collectors.

And those chatting about Absorption or adsorption cooling/AC, we are deep into this at the moment, to be released next year. One common misconception is PV is a better deal. Only rarely will this happen. A. The area for the PV panels is 4X greater, B. A PV system requires batteries typically to run at night, C. 4X the PV system greatly reduces the cost benefit, and if we are talking about a AC with a compressor, most people forget about the huge draw when starting up. This means the PV system must be over sized by over 150%/r as a rule. ST however can easily store heat or cooling, and store cooling. It not as efficient as a compressor but it doesn’t have to be.