Energy Return on Energy Invested for Solar PV

tahanson43206 · 2024-04-08 10:59:37

For SpaceNut re #50

Thanks for your helpful prediction.... free carbon might indeed try to bond to the metal walls of the coolant lines. On the other hand, the free hydrogen would be looking for carbon atoms at those temperatures. While I think your prediction has merit, it seems to me it is a hypothesis that would need to be tested in a live system. There may have been experiments already performed and documented.

Please look for any reports of testing hydrocarbon materials used as heat transporters.

Calliban has predicted that hydrocarbon materials would disassociate at high temperatures. What is not clear is what would happen to the free atoms as conditions become cooler, as would happen as the material moves through the radiator part of the line.

The ideal result would be formation of new hydrocarbon molecules, which would release thermal energy that would itself transfer to the outside heat sink.

What (I think) we are describing is a kind of phase change operating at elevated temperatures.

It should be possible for our NewMars members to find out what actually happens.

NewMars members occasionally indulge in speculation. This would be a good opportunity to replace speculation with research.

(th)

SpaceNut · 2024-04-08 11:14:08

A catalyst is required to recombined, free hydrogen back to the desired chain. That would interfere with the circulation pf the working fluid.

kbd512 · 2024-04-08 17:22:32

Calliban,

The short answer is that yes, corrosion and embrittlement will become problems over time, but that is why advanced aerospace coatings were invented. A low alloy steel like Eglin ES-1, yields at 191,000psi at 482C. With a good ceramic coating baked onto an ion-bonded coating underneath, would do wonders for service life. Creep strength becomes a real problem at very high operating temperatures and pressures, but the salt wouldn't be pressurized at all, so only the corrosive effects and metal expansion / contraction are problematic.

kbd512 · 2024-04-08 17:25:04

tahanson43206,

Ivanpah and Crescent Dunes solar generating stations use molten salt for their thermal energy storage. Crescent Dunes was shut down due in 2019, I think, following a failure to produce some specified amount of power at a specified cost. They made a big deal about the cost of Crescent Dunes power ($135MWh vs $30MWh for photovoltaics), which utterly ignores the fact that the photovoltaics have no storage at all included in their cost model. At the time of shutdown, Crescent Dunes was producing a record amount of power, it was fully functional, and it stores 10 hours worth of power (1,100MWhe), with a nominal plant output of 110MWe. There was a structural failure of the molten salt tank there in prior years, 2016 I think, which was repaired. As with all first generation technology, there are lots of unknowns. They failed to account for the rate of thermal expansion at the base vs walls of the molten salt tank. It resumed production in 2020 or 2021 under new management.

There are no photovoltaic generating stations storing 10 hrs of electrical power using batteres, because doing so immediately and drastically increases their costs, beyond the cost of solar thermal with storage. Multiply the cost of the batteries, Sodium-ion or Lithium-ion, by 10hrs, and each hour of 110MWe output (what Crescent Dunes was producing), requires dramatically more cost per MWh of power delivered.

kbd512 · 2024-04-08 17:26:54

Cost Projections for Utility-Scale Battery Storage: 2023 Update

Figure ES-2 shows the overall capital cost for a 4-hour battery system based on those projections, with storage costs of $245/kWh, $326/kWh, and $403/kWh in 2030 and $159/kWh, $226/kWh, and $348/kWh in 2050

Now multiply those estimates by 2.5X, because that's how much power Crescent Dunes was generating for most of an entire day. $135/MWh, all-in cost to deliver power to the grid, for what was essentially a one-off prototype project attempted 10 years ago, was a miracle.

Would you rather pay $427.5/MWh, or $0.4275/kWh (photovoltaic plus 10 hours of full output storage), or $0.135/kWh (solar thermal plus 10 hours of full output storage)?

Calliban · 2024-04-09 03:45:37

kbd512 wrote:

Calliban,
The short answer is that yes, corrosion and embrittlement will become problems over time, but that is why advanced aerospace coatings were invented. A low alloy steel like Eglin ES-1, yields at 191,000psi at 482C. With a good ceramic coating baked onto an ion-bonded coating underneath, would do wonders for service life. Creep strength becomes a real problem at very high operating temperatures and pressures, but the salt wouldn't be pressurized at all, so only the corrosive effects and metal expansion / contraction are problematic.

Low alloy steels should retain adequate strength for non-pressurised pipework at 500°C. We would coat the tubes both internally and externally, to resist oxidation. These steels are really cheap and easy to manufacture and recycle.
https://www.engineeringtoolbox.com/meta … _1353.html

kbd512 wrote:

Ivanpah and Crescent Dunes solar generating stations use molten salt for their thermal energy storage. Crescent Dunes was shut down due in 2019, I think, following a failure to produce some specified amount of power at a specified cost. They made a big deal about the cost of Crescent Dunes power ($135MWh vs $30MWh for photovoltaics), which utterly ignores the fact that the photovoltaics have no storage at all included in their cost model. At the time of shutdown, Crescent Dunes was producing a record amount of power, it was fully functional, and it stores 10 hours worth of power (1,100MWhe), with a nominal plant output of 110MWe. There was a structural failure of the molten salt tank there in prior years, 2016 I think, which was repaired. As with all first generation technology, there are lots of unknowns. They failed to account for the rate of thermal expansion at the base vs walls of the molten salt tank. It resumed production in 2020 or 2021 under new management.

The $30/MWh figure for PV is a LCOE value that was calculated before interest rate rises came into effect. The Chinese have reduced purchase prices of panels by establishing manufacturing facilities using zero interest rate loans, employing slave labour and using stranded coal to produce power for the polysilicon factories. Anything can be made cheaply under those conditions. But it clearly isn't sustainable or ethical. I find it amazing how easily people can turn a blind eye to unethical practices when it suits them. These are the same people that will call you a Nazi if you want more robust immigration controls. At the same time, they are promoting a product that is made by slaves.

Solar thermal power isn't yet being manufactured at levels high enough to reap economies of scale. When it is, simple aluminium coated steel reflector panels are going to be a lot cheaper and easier to make than slabs of doped semiconductor. The materials involved are very cheap and abundant.

If molten salt thermal energy storage can extend capacity factor to 80% or more, then OCGT can provide a low cost backup solution.
https://energyforgrowth.org/article/sho … -turbines/

Last edited by Calliban (2024-04-09 04:32:44)

tahanson43206 · 2024-04-09 06:23:14

I'm hoping someone can find documentation of how a material that is solid at room temperature is put into service and kept molten.

The procedure needed if a facility is going to be cooled down (as would happen with solar powered heating equipment) would presumably involve drawing molten material into a holding tank.

If there is a facility in operation today, those operating procedures must be in place.

If anyone has discussed practical operation of a system like this, I've missed it.

In the US West in the past, and perhaps even today, it was necessary to keep a supply of fresh water next to a pump in the desert, so that there was water to provide suction for the pump. It was customary to fill the supply vessel after drawing water, so the next visitor could use the pump.

Perhaps something similar is needed for operation of a system that uses molten salt as a working fluid.

(th)

Calliban · 2024-04-09 08:55:25

TH, that is an interesting point that we have glossed over until now. What happens if the HTF freezes in the pipes? Is that something that will cause problems? Obviously, it would destroy impulsive pumps if solid particles entered them. What about the trough tubes, fluid mains and heat exchangers? I don't think salts expand as they freeze. So freezing won't burst the tubes. Would it mechanically stress components? Would it damage protective coatings? I don't know. If the fluid did freeze, it would complicate restarting the pumps. We would as you say, need a system that either drains fluid into a tank where it stays liquid after sundown, or build the system to allow natural circulation to remelt the salt prior to restart. If the salt melting point is substantially beneath operating temperature, we could keep it liquid using a thermal capacitance of some kind. This is definitely an important design question.

Last edited by Calliban (2024-04-09 08:58:02)

kbd512 · 2024-04-09 09:27:16

tahanson43206,

Are you familiar with how humans heat ice water to make liquid water during winter camping?

Ordinarily, people use Propane to heat the water, which becomes a solid due to the drop in temperatures associated with "winter", so they light a fire under the "frozen water", until it melts and then boils. The water could be heated with a fresnel lens, which would also work, but most people tend to be very impatient, so they use natural gas in their home or Propane when outdoors. They frequently burn wood or coal as well.

The Sodium Nitrate / Potassium Nitrate molten salt mixture is heated up one time using natural gas, to a temperature above 260C, at which point it becomes a liquid or "molten" salt. After that, sheer thermal mass and the constant re-injection of heat energy from the Sun keeps the salt in a liquid or molten state. Remember that old cube-square law, which states that for an increase in volume, while internal volume increases significantly, surface area doesn't increase at the same rate? That's the same one you're taking advantage of by having a lot of thermal energy storage mass to "sink" all that solar heat into. Since the salt is very cheap, relative to any kind of battery or photovoltaic device.

Sodium Nitrate and Potassium Nitrate both cost about $800 per metric ton in Q4 2023 prices. There is no shortage of either material, nor will there ever be. Sodium, Potassium, and Nitrogen are very common materials.

This is from National Renewable Energy Laboratory / "NREL", in 2017:

Every day, enough energy is stored at Crescent Dunes to match all of the utility-scale batteries in global operation—combined—at a fraction of the cost and with no degradation or replacement issues.

Here's a quote from a research paper about Crescent Dunes:

The result showed that the annual average capacity factor is 91.4% thanks to the oversizing of the solar field and the thermal energy storage by molten salt.

Each tank of molten salt, of which there are 2 tanks at Crescent Dunes, a "hot tank" at 566C and a "cold tank" at 260C, holds 52,000t of salt mixture.

104,000t * $800/t = $83.2M for all the salt used by Crescent Dunes, at Q4 2023 prices

Salt will remain salt, at the temperatures involved, until the end of time, meaning even after you shut down the plant, the salt can be dumped into the next power plant's storage tank. That's how you "recycle" the salt when the plant inevitably gets old and has to be rebuilt. 10,000 years later, the salt will still be salt, so if you dump it into the next solar thermal energy storage system, it will continue to store heat energy from the Sun.

104,000t of salt = 1,100MWhe, with 2,685kWh/m^2/year of direct solar insolation, where Crescent Dunes is located, so 10,577Whe in terms of stored heat energy, when converted into electricitiy using traditional steam / water in the plant's salt / water heat exchanger that powers the electric generator portion of the solar thermal power plant.

If someone manufactured Sodium-ion batteries for $50/kWh, they would cost $55M for 1,100MWhe. That's the cost for the battery, though, not the cost for a battery storage subsystem connected to a reliable electric grid. The most optimistic battery cost projections into 2030 by NREL, are $159kWh for a battery with all the equipment to connect it to the power grid, so $159M for 1,100MWhe of energy storage. In 10 years, you're going to pay another $159M. Even if the cost comes down by a factor of 10, you already paid $159M, plus the cost of brand new batteries every 10 years. All costs are additive over time, so even if Sodium-ion batteries cost 15.9M, rather than $159M, for the same storage capacity, $15.9M * 7 replacements per 70 year human lifetime = $111.3M. If NREL's estimate is reflective of reality on the go forward, then $1,113M over 70 years. This is a losing game, only played by people who are exceptionally poor at math and economics. Sadly, that describes most people. Current battery prices are about double the optimistic $159/kWh 2030s NREL projection. On top of that, if you discharge 100% of the battery capacity every day to provide power when the Sun doesn't shine, it will never last 10 years. It may not last 2 years. That means you need twice as much battery capacity.

Salt becomes progressively cheaper over time because it never "wears out" like an electrochemical battery. Even Sodium-ion batteries "wear out" over time. After you collect the salt, the monetary and energy debt incurred to "make" the salt has been paid for. The only way you will ever "pay twice" or "pay again" for the same batch of salt, is if you dump the salt into the ocean and start over again by making a fresh batch of salt. Since there's no plausible reason to do that, salt is something you pay one time for, in terms of money and energy, and then get to use the salt to store heat energy ever after.

Since all power plants do wear out over time, how fast that happens drastically affects total costs, paid for in terms of input money and embodied energy and labor, over time. A thermal power plant based upon, coal, gas, nuclear, or solar, is only built once per human lifetime. Photovoltaics, wind turbines, and especially electrochemical batteries, must be remanufactured multiple times over a single human lifetime. Signing up for that insanity is a better than average way to remain in perpetual energy and monetary poverty, but not a good way to run a flourishing human civilization with abundant and comparatively "clean" power. That means energy, money, and labor expenditures over time are important, despite the pervasive human propensity for very short-term thinking. These concepts are even more important if you want actual progress towards the goal of reducing hydrocarbon energy consumption. As of right now, there's no measurable progress towards reducing global CO2 emissions, because we're burning anything that burns to make a lot of very short-lived electronic energy generating and consuming devices that are energy intensive to make. Energy policy shouldn't be the domain of short term thinkers.

kbd512 · 2024-04-09 09:34:07

Here's a brochure from Solar Reserve explaining how the Crescent Dunes power plant functions:

Solar Reserve - Crescent Dunes

tahanson43206 · 2024-04-09 09:35:58

For Calliban re #58

Thank you for your support of this inquiry! There seems to be a lot of potential for solar thermal, and recent posts seem to show that there is some serious development going on. I'm hoping that our members will post news and links to resources to this topic.

In the case of a reactor, once heating starts it won't stop for a while, so the issue of solidification of coolant seems less likely to be a concern, but for a solar facility it would be an issue each day.

My guess is that operators might choose to use a coolant with a freezing point below ambient temperature even if the system performance is a bit less impressive than it would be with molten salt.

You have raised the issue of disassociation of carbon and hydrogen if hydrocarbon coolant is driven to temperatures at the high end. I have not yet seen a definitive analysis of what to expect. SpaceNut took a first look at the problem, with a question about carbon possibly caking on the interior of lines. I'm less sure, since the hydrogen would be there looking for carbon atoms, so it is possible that hydrocarbons would form naturally as the coolant cools in the secondary heat transfer system. In other words, there may not be a problem at all.

This question will remain pending for a while, but eventually we should be able to find a post an answer.

(th)

Calliban · 2024-04-09 10:45:06

The molten salt stored in the tanks is a form of sensible heat storage, as there is no phase change involved. We could make sensible heat storage even cheaper by passing the molten salt through tanks containing crushed rock. Crushed rock or concrete is almost free and is often a waste stream from mining or demolishion. I imagine that they would have considered that in the design process. Maybe the salt was already cheap enough.

A solar thermal system actually benefits from three types of energy storage. It has the heat capacity of the salt, the heat stored in saturated water within its boilers and the rotational energy within its turbine. Collectively, these provide the plant with a 91% year round capacity factor. That is very impressive. It means that backup powerplants can be low cost GTs without too much concern for fuel efficiency.

The Crescent Dunes powerplant was a tower type collector. But the same design principles could apply to a trough based system with a slightly lower temperature salt. Interestingly, different parts of the plant will have different life expectancy. The turbogenerator sets and salt storage tanks should last adequately for 60 years. The boilers may need replacing before then, due to corrosion from dissolved oxygen in saturated hot water. Chemistry control has improved a lot over the past fifty years. The condenser tubes may require earlier replacement for much the same reason.

It would appear that the basic elements of this technology are well developed. What is now needed is a simplified trough based design that is suitable for mass production, modularisation and rapid build and comissioning. Costs should come down as mass production is applied to modular components and as build times are reduced by an experienced workforce.

Last edited by Calliban (2024-04-09 10:51:04)

Terraformer · 2024-04-09 11:21:56

If we really wanted to go low embodied energy for solar... could the mirrors for a compact linear fresnel reflector be made out of wood and foil? The strength requirements should be a lot lower than for a parabolic trough, and the mirrors are either flat or slightly curved. AFAICT the mirror slats themselves are adjusted to account for changing solar angle.

tahanson43206 · 2024-04-09 12:42:30

For Calliban re #62

thanks for the link to the Wikipedia article on the Cresent Dunes project...

Excess thermal energy is stored in the molten salt and could be used to generate power for up to ten hours, including during the evening hours and when direct sunlight is not available.[5] The storage technology thus eliminated the need for any backup fossil fuels, such as natural gas. Melting about 70,000,000 pounds (32,000,000 kg) of salt took two months. Once melted, the salt stays melted for the life of the plant and is cycled through the receiver for reheating.[34]

The quoted citation hints at how the builders addressed the issue of salt solidifying.... Apparently they planned to keep the material hot enough so it never solidified.

The plant has been running and stopped several times. One failure (in 2016) was a failure to plan for stress on the base of the molten salt tank due to thermal cycling. The plant leaked, so the operation has to be discontinued. That is an interesting design problem, and clearly the original engineers did not provide enough strength in the wall of the container to hold up. I assume that since the system resumed operation a stronger base must have been designed and installed.

The plant appears to have been designed and possibly built by a company with experience in Spain. The challenges of building a plant on the scale of this one clearly overwhelmed the original management team.

As near as I can tell, the plant appears to be operating, but it appears to be less productive than had been hoped.

Per Google:

About 45,700 results (0.36 seconds)
Operational concentrating solar thermal power plants like Gemasolar or Crescent Dunes use a NaNO3-KNO3 mixture (composition by weight 0.60–0.40) called 'Solar Salt' as the heat transfer fluid (HTF) and as the storage medium.
Performance of molten sodium vs. molten salts in a packed ...
ScienceDirect.com
https://www.sciencedirect.com › article › abs › pii

Here is an article that appears to address the issue of molten salt freezing ... apparently there are "solutions" to keep salt molten ...

https://www.sciencedirect.com/topics/en … trate-salt

6.7.3 Molten salt technology
Molten nitrate salt is the current preeminent storage medium. It has been demonstrated in troughs at lower temperatures and towers at 550°C. At the higher temperatures, the amount of salt required to store heat is substantially reduced through a larger temperature difference (close to a factor of 3) so that the plant can follow the load precisely by storing any excess energy in the molten salt tank.
In the last decade, parabolic trough operation with molten salt circulation operating at 550°C has been demonstrated, with suitable receivers and solutions against salt freezing in the field at night and overnight heat loss. LFC using the same receiver technology certainly seems a superior configuration as it offers fixed piping easily heated by reflectors and excellent drain-down possibilities. At temperatures of 550°C, heat loss is important, and the higher concentration of LFCs would reduce that liability relative to a trough. Out of this motivation prototypes of molten salt, LFC technology has been developed and investigated by at least two companies over the last 5 years. In China, the commercial Lanzhou Dacheng Dunhuang 50 MWe Molten Salt Fresnel Concentrated Solar Power Project has been reported to be successfully connected to the grid at the end of 2019 (Reve, 2020).

(th)

tahanson43206 · 2024-04-09 12:44:36

For Terraformer re #63

Speaking of Fresnel systems...

https://www.sciencedirect.com/topics/en … trate-salt

Linear Fresnel Collector (LFC) solar thermal technology
Werner J. Platzer, ... Wilson Gardner, in Concentrating Solar Power Technology (Second Edition), 2021

If this work is of interest, please report on it.

I found this while looking for information about how plant operators deal with solidification of salts used for thermal energy transport and storage.

(th)

kbd512 · 2024-04-09 12:46:44

Calliban,

Even at the same operating temperatures that would work well for steam, supercritical CO2 still offers an additional 2% to 4% efficiency improvement. I understand that water is very desirable for engineers to work with because it's so well understood and does have many desirable qualities, and it's also tradition, but the size of the equipment is a problem. The greatest advantages of supercritical CO2 are the 10X reduction in the size of the turbo and the 8X reduction in size for diffusion-bonded printed circuit heat exchangers. We're going to need a lot of these power plants if we use the Sun or the Earth as our primary energy source, which is why the size of the machines, what they're made from, how long they last in operation, and plant capacity factors matter so much. I doubt that water will be less corrosive than CO2 at the temperatures involved.

90% capacity factor should be a standard metric by which these renewable energy power plants are judged, in terms of dollars spent per Watt-hour of energy produced, over at least 75 years. We're going to run these machines until the proverbial wheels fall off, because that's the only way we can recoup the energy and time spent producing them while also generating a sufficiently large energy surplus to make them worth having. That greatly limits the tradespace of workable ideas and acceptable ways of doing things. Any capacity factor over 90% is nice to have, but not if it requires specialty materials, gobs of control electronics, or reduced service life of the equipment. After we deploy enough of these systems, we won't need backup power plants. That is the ultimate idea- energy generating systems that are self-contained to the point that they generally don't require multiple levels of backups, all of which consume energy, materials, money, and labor. For now, we will require backups, but that is another area where we're working on sCO2 turbines. There are pintle gas injectors for Oxy-Fuel operation of supercritical CO2 turbines, such that no backup turbines are required. If the solar power, molten salt energy storage, or whatever else in the plant fails, then it reverts back to using natural gas fuel to power the generating turbines. That said, there's no separate turbine. It's the same turbine, using thermal power from the Sun whenever possible, and natural gas as a backup if solar power ever fails.

There does not need to be absolute electronically-controlled precision perfection here, if that also means the plant is totally non-functional the moment those electronics fail or get zapped by something. There should be two operators in a control room with a pair of iPads who use their fancy electronics to monitor but not control the plant, except for what percentage of the plant's electrical output is dumped into the ground when it cannot be used or stored. That cannot be done with the degree of precision required, absent autonomous electronic control. If dumping exceeds 5% of the plant's annual output, then we need to add more storage. We should probably include 10% more storage than we think is strictly necessary, as a sort of "fudge factor" allowing us to absorb a little bit more power. The non-electrical / non-electronic hydraulic heliostat Sun trackers I posted about in another thread will control mirror positioning. Since they lack any electronics or even electrical motors, they simply cannot fail due to electronic controller or electric drive motor short-circuit. They're probably not as precise as electronically-controlled systems, but that's not why they're being selected. They're simple hydro-pneumatic devices capable of generating very large torque inputs into the heliostat mirror drives, and they track the Sun without the use of electronics. They contain about as many parts as a pair of shock absorbers on a car.

Calliban · 2024-04-09 16:50:15

This paper describes the S-CO2 cycle in some detail.
https://dspace.mit.edu/handle/1721.1/17746

At 550°C with a 20MPa turbine inlet pressure, cycle efficiency is 45.3%. If turbine inlet temperature can reach 650°C, then efficiency would be as high as 50%. But material strength becomes a problem at those temperatures. At 550°C, steels retain enough strength to be usable. But the strength of most steels falls off a cliff at temperatures above 600°C.

I hadn't though about including an option for directly firing the S-CO2 cycle using natural gas. This would appear to be a more cost effective option than having a seperate GT for the 10% time that the solar plant is unavailable.

kbd512 · 2024-04-10 00:13:33

Calliban,

Here's some of the current development work:
Development of Oxy-fuel Combustion Turbines with CO 2 Dilution for Supercritical Carbon Dioxide (sCO2) Based Power Cycles

General Electric's development efforts:
Novel Modular Heat Engines with Supercritical CO2 Bottoming Cycle Utilizing Advanced Oil-Free Turbomachinery: PHASE 2

SpaceNut · 2024-04-12 16:13:10

Concentrating Solar-Thermal Power Introduction

tahanson43206 · 2024-04-12 17:29:29

For all re SpaceNut's post #69

Slide 18 shows the CO2 turbine that kbd512 has been discussing.

(th)

New Mars Forums

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#51 2024-04-08 10:59:37

Re: Energy Return on Energy Invested for Solar PV

#52 2024-04-08 11:14:08

Re: Energy Return on Energy Invested for Solar PV

#53 2024-04-08 17:22:32

Re: Energy Return on Energy Invested for Solar PV

#54 2024-04-08 17:25:04

Re: Energy Return on Energy Invested for Solar PV

#55 2024-04-08 17:26:54

Re: Energy Return on Energy Invested for Solar PV

#56 2024-04-09 03:45:37

Re: Energy Return on Energy Invested for Solar PV

#57 2024-04-09 06:23:14

Re: Energy Return on Energy Invested for Solar PV

#58 2024-04-09 08:55:25

Re: Energy Return on Energy Invested for Solar PV

#59 2024-04-09 09:27:16

Re: Energy Return on Energy Invested for Solar PV

#60 2024-04-09 09:34:07

Re: Energy Return on Energy Invested for Solar PV

#61 2024-04-09 09:35:58

Re: Energy Return on Energy Invested for Solar PV

#62 2024-04-09 10:45:06

Re: Energy Return on Energy Invested for Solar PV

#63 2024-04-09 11:21:56

Re: Energy Return on Energy Invested for Solar PV

#64 2024-04-09 12:42:30

Re: Energy Return on Energy Invested for Solar PV

#65 2024-04-09 12:44:36

Re: Energy Return on Energy Invested for Solar PV

#66 2024-04-09 12:46:44

Re: Energy Return on Energy Invested for Solar PV

#67 2024-04-09 16:50:15

Re: Energy Return on Energy Invested for Solar PV

#68 2024-04-10 00:13:33

Re: Energy Return on Energy Invested for Solar PV

#69 2024-04-12 16:13:10

Re: Energy Return on Energy Invested for Solar PV

#70 2024-04-12 17:29:29

Re: Energy Return on Energy Invested for Solar PV

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