Solar energy at home.

[voodooless]

It's better than generating cold -- that darned thermodynamics thing gets you, every time!

Not really. Generally a heat pump will be more efficient generating cold than heat. Cooling COP is often more than 4, while heating will be 3 or worse. Thermodynamics indeed!

 

[ianovic69]

Very interesting reading through the replies in this thread.
I've not been able to find anything much about using a ground source heat pump just for making electricity to battery storage.
Potentially it could be to run an electric heating and hot water unit, but if that's not feasible then just the electric would be fine.
I haven't yet talked to any installers as I'd like to have some idea what I'm asking beforehand, which is why I'm asking here first.
Any info would be greatly appreciated. Thanks in advance.

 

[Osvaldo de Garay]

As I studied in the school several years ago, you need a large temperature difference to make efficient the conversion into electricity. In other words, the temperature gradient.
As an example, in a car, what produces the movement is the big adiabatic gradient into the cylinder what causes the expansion of the gasses and in turn, movement of the shaft. The same happens in the large nuclear or thermoelectric converters (please, note that ENERGY isn't generated or wasted, is converted into a different form of energy: in a resistance into heat, in a speaker, into acoustical).

So, really I am skeptic about a reliable way of convert a 30 or 40°C gradient into electrical energy.

Sun light is about 1KW/m² taken the average about the entire Earth and all the year. The usual efficiency of a solar panel like mines, are about 13~15 % so we can get about 150W/m² average. Ergo we are talking about interesting values.

There actualy are being manufacturing better technologies about solar cells, but stilltoo expensive for my pockets, and one really don't need a 40% efficieny unless you depend exclusivelly from them.

 

[Imakeller]

Very interesting reading through the replies in this thread.
I've not been able to find anything much about using a ground source heat pump just for making electricity to battery storage.
Potentially it could be to run an electric heating and hot water unit, but if that's not feasible then just the electric would be fine.
I haven't yet talked to any installers as I'd like to have some idea what I'm asking beforehand, which is why I'm asking here first.
Any info would be greatly appreciated. Thanks in advance.

Geothermal is super efficient heating, but I’ve never heard of using that type of system for producing electricity. Solar is a tried and true method.

 

[voodooless]

There actualy are being manufacturing better technologies about solar cells, but stilltoo expensive for my pockets, and one really don't need a 40% efficieny unless you depend exclusivelly from them.

Your 27 panels could easily be replaced with a single modern panel for less than $65 or so, with less surface area used (23% efficiency or so).

 

[MCH]

I am having this dilemma from some months now, and I never thought ASR could be a place to ask.... but everywhere else I asked, the answers become fast political and are of little help.

Ok, the economic side:
I live in Luxemburg and even though my roof has a pretty good orientation and the government helps with the initial investment, the climate and the incredibly high installation prices vs neighbor countries make that we would need 7-10 years to break even, and at that point we might have to start thinking on replacing the battery (? not sure what is the state of the art). All in all it seems a pretty bad investment on my book.

People tend to counter this saying that the panels allowed them to have the AC running full power all summer, but we are more windows wide open kind of people, I wouldn't want air conditioning even for free.

On the environmental side things get much more complex, and this is the part I struggle more having a meaningful conversation with anyone, as people tend to rely on very simplistic arguments.
Filling the house with hundreds of kg of electronics, batteries and structural elements that for sure carry a heavy footprint to have them working well below their possibilities in central Europe doesn't seem like a no brainier to me unless someone shows me the numbers. And most especially when a good chunk of the electricity we buy today is from renewable sources. I know there are a lot of caveats here,and that my money will also help suppliers to keep advancing the technology, but my point is that I don't have enough information to make an informed decision.

Another argument to postpone the investment is the expectation that the technology evolves further, especially on the battery side. Also reverse charging (or whatever it is called) using a car battery sounds attractive, but is not available where we live at the moment.
Would love to hear your opinions and would love to be proven wrong. Thanks!

 

[Osvaldo de Garay]

Your 27 panels could easily be replaced with a single modern panel for less than $65 or so, with less surface area used (23% efficiency or so).

My problem is mechanical and environment. I haven't sufficient skills and tools in Mechanics as to build a large and safety supporting armature. Also, I am co-propietary of my house with who live under me. So I need to build a flat surface with little resistance to wind. It's true that I can put a newer and bigger cell, but it becomes difficult for me to put it in action. All this to avoid problems. Fortunately I live upstairs, so vandalism is difficult.

 

[Osvaldo de Garay]

Would love to hear your opinions and would love to be proven wrong. Thanks!

I'm very satisfied with what I could build. I started with 1, 2, 3, 6, 12, 18, 24 and finally the actual 27 units. I grow them as I saw the necesity. But in this middle time, the small fridge with the 12/24VDC Sikelan compressor was owned, I need to give a bigger steep in the power installed. It drains about 5 amper @12V averaging a 0.45 duty at year, so it is my best energy eater. The ham radio rigs don't need too much power nor internal lightning.

I haven't installed a commercial inverter nor I will do. Those devices are big current demmanders as their own, as there is a large logic controlling IGBT's, relays, wonderfull screens, leds, wifi or blue tooth remocons, and the like. And when I repaired some of them in my last job, my experience is that they are intrinsecally fragile as all the power is managed by chips of sand. Another point, are storms. Electric storm impacting in power grid cause immediate semiconductor blown, and all your effort and money goes into smoke in microseconds. That's why my installation is (and will be) off-grid.

Also, when your apparatus is sending energy into the the grid, it needs to be perfectly synchronized with grid, both at phase and in voltage. A minimal error caused by noise that lacks synch even for milliseconds, all is quickly converted into carbon.

 

[mhardy6647]

With high voltage DC on one side of the panels... vandalism invites Darwinian selection -- at least when the sun's out!

 

[Osvaldo de Garay]

Not my case. All 27 cell are parallel wired, so total voltage under no load reaches 22 or 23V at best. But the issue is misseducation of guys who can throw stones into them. My pieces are unviewable from street.

 

[MCH]

I'm very satisfied with what I could build. I started with 1, 2, 3, 6, 12, 18, 24 and finally the actual 27 units. I grow them as I saw the necesity. But in this middle time, the small fridge with the 12/24VDC Sikelan compressor was owned, I need to give a bigger steep in the power installed. It drains about 5 amper @12V averaging a 0.45 duty at year, so it is my best energy eater. The ham radio rigs don't need too much power nor internal lightning.

I haven't installed a commercial inverter nor I will do. Those devices are big current demmanders as their own, as there is a large logic controlling IGBT's, relays, wonderfull screens, leds, wifi or blue tooth remocons, and the like. And when I repaired some of them in my last job, my experience is that they are intrinsecally fragile as all the power is managed by chips of sand. Another point, are storms. Electric storm impacting in power grid cause immediate semiconductor blown, and all your effort and money goes into smoke in microseconds. That's why my installation is (and will be) off-grid.

Also, when your apparatus is sending energy into the the grid, it needs to be perfectly synchronized with grid, both at phase and in voltage. A minimal error caused by noise that lacks synch even for milliseconds, all is quickly converted into carbon.

I think some self-installed panels are allowed where I live, but only up to a certain power. But my roof is not flat and I would need professional help anyways (=$$$$)

 

[ianovic69]

This is UK info but may be interesting for some -

Plug-in solar panels explained

Plug-in solar panels are small DIY renewable systems that can be installed in a sunny spot of your choosing with a cable that plugs straight into your typical 3-pin socket.

octopus.energy

 

[voodooless]

I think some self-installed panels are allowed where I live, but only up to a certain power. But my roof is not flat and I would need professional help anyways (=$$$$)

Sadly, with costs for the panels being very low, the installation costs are relatively high, often almost 50% of the total cost. I've done the full install myself, including the battery, and that makes the whole thing a lot more economical. Only installed on my flat roof, though, where I can safely operate.

My problem is mechanical and environment. I haven't sufficient skills and tools in Mechanics as to build a large and safety supporting armature.

If you can build 27 small ones, you can build one larger one. Honestly, if you just lay the big panel flat on your roof, you'll probably get better yields than you have right now.

 

[ianovic69]

As I studied in the school several years ago, you need a large temperature difference to make efficient the conversion into electricity. In other words, the temperature gradient.
As an example, in a car, what produces the movement is the big adiabatic gradient into the cylinder what causes the expansion of the gasses and in turn, movement of the shaft. The same happens in the large nuclear or thermoelectric converters (please, note that ENERGY isn't generated or wasted, is converted into a different form of energy: in a resistance into heat, in a speaker, into acoustical).

So, really I am skeptic about a reliable way of convert a 30 or 40°C gradient into electrical energy.

Sun light is about 1KW/m² taken the average about the entire Earth and all the year. The usual efficiency of a solar panel like mines, are about 13~15 % so we can get about 150W/m² average. Ergo we are talking about interesting values.

There actualy are being manufacturing better technologies about solar cells, but stilltoo expensive for my pockets, and one really don't need a 40% efficieny unless you depend exclusivelly from them.

Yeah heat pumps work like a fridge in reverse, and on a much bigger scale. The ground source type are either bore hole pipes or a lattice laid about 1 to 2 metres under your lawn.
The unit is like a big fridge and would usually replace the gas/oil boiler. It's expensive to install but can generate large amounts of continuous, renewable electricity.
I'm trying to avoid solar, despite my property being perfect for it. We use oil currently which I want to replace but I don't know if it's possible.
I think I may have to contact some installers....

 

[voodooless]

Yeah heat pumps work like a fridge in reverse, and on a much bigger scale.

It's expensive to install but can generate large amounts of continuous, renewable electricity.

A heat pump does not generate electricity. It generates efficient heat or cooling, depending on how it's configured.

Electricity can be generated via a geothermal power plant. A bit of pipe under your lawn won't cut it. You'll need to be very deep to get to much higher temperatures for this. This isn't exactly consumer level technology

 

[Osvaldo de Garay]

My roof has an angle of ~20° to the west. So if I allocate one or more cells parallel to the roof, the sun never impacts normally to them (90°) so the efficience allways be lower than my sunlight orientated actual tiles. Also, the chances of breakage during a storm with hail is unmensurably higher. Mines are about 45° so the hail bounce away.

Again, it isn't economically possible to change them now, I lost job at 2020 during pandemia, and nowadays with 57 and a large unemployment, the possibility to fing a new job is remote.

 

[MCH]

We are very happy with our heat pump, without any previous reference though. The coldest winter months draws a continuous below 1kw and heats all the 220m2 house + hot water. (It is air/water)

 

[voodooless]

Again, it isn't economically possible to change them now

Probably not. Whatever you already have for will be the most economical to keep. Now if you would expand, that would be another matter.

 

[mhardy6647]

Sadly, with costs for the panels being very low, the installation costs are relatively high, often almost 50% of the total cost. I've done the full install myself, including the battery, and that makes the whole thing a lot more economical. Only installed on my flat roof, though, where I can safely operate.

Yup.



PS There is one major drawback to roof-mount PV panels, at least where we live...

 

[Imakeller]

Yup.



PS There is one major drawback to roof-mount PV panels, at least where we live...

With that much property, why didn’t you go with ground mounted PV arrays?