Hello, I'm new to the forums. I would like some insight on safe solar storage. I've done quite a lot of research on this for cheap ideas for long term safe storage and thought of a system I would use. I'm looking for extra knowledge of problems that could occur with the system I am planning on building with a new house build. Also to help people think up an inexpensive way to do solar storage.
- I am going to put parabolic mirrors to track the sun on my roof with pipes running through them, in the pipes will be oil ( I haven't decided what type of oil yet, maybe you could give me an idea ).
- I'm going to install a control system ( maybe reliable controls ) to control the output oil temperature to 390 Deg. C.
- The oil will go down to a room with a very large cylindrical cement casing, covered in insulation. In the cement structure will be sand or salt ( the cheaper one of the two ), the oil will discharge it's heat into the sand or salt.
- That heat will be extracted later when needed for in floor heating, DHW (Domestic hot water) heating, heat pump loop heating and electricity. Therefore this mass has to be big.
- Extracting heat for in floor heating, DHW, and the heat pump loop heating is straight forward, but for electricity it is not, as many of you may know, it is quite difficult to get electricity out of heat with a cheap method.
- Here is what I thought up, I would use thermoelectric modules. I'm looking to cover an area of 50 cm x 50 cm, with approximately 60-90 modules ( I would need the test the modules before buying them in large quantities). These modules will then be placed against a heat exchanger extracting heat from the sand and the opposite side of the module will be against a cooling side. The cooling side will be feed by glycol from stored cooling provided by the PV solar. I will incase them in a container and create a vacuum to avoid too much heat leakage.
PROS and CONS
PROS
- Safe
- Most simple in design
- Most inexpensive storage to all the other systems out there
- Less parts
- Less parts to wear, corrode, or fail.
CONS
- Inefficient electrical use
- I don't know the breakdown of oil, but it may need to be changed after a few years.
That is my idea of the system I'm going to build, I have looked thoroughly at HHO storage, H2/O2 storage, flywheel storage, battery storage, molten salt storage, kinetic water storage, use of a stirling motor and kinetic storage in general. Most of these ideas are very expensive in the long run and have to many parts involved. I wanted to simplify the system as much as possible and keep it cost effective.
When I build the system (maybe in 2 years time, I need to design the house around this) I will definitely post everything I'm doing on youtube for everyone in the world to use it, if it is feasible.
Let me know what you think
Mechster
Hi mechster
I like the idea of mirrors & tracking the sun, I'm doing it with Solar Heliostats we call Sunflowers.
I've made 20 so far as prototype / proof of concept, & instead reflect the energy to a fixed focal heat exchanger that will use Hot Air so there will be no liquid leaks & loss of function. The heat storage will be " rocks " Halibuton Granite " is locally available in smooth fist size rocks, the space between them will allow the Hot Air to flow around them & exchange heat. for insulation
Rockwool of 1 ft thickness, air manifold can direct heat where needed, modular Heliostats can be added if more energy is required.
Regards
Peter
Quote from: mechster on September 05, 2014, 09:37:24 AM
Hello, I'm new to the forums. I would like some insight on safe solar storage. I've done quite a lot of research on this for cheap ideas for long term safe storage and thought of a system I would use. I'm looking for extra knowledge of problems that could occur with the system I am planning on building with a new house build. Also to help people think up an inexpensive way to do solar storage.
- I am going to put parabolic mirrors to track the sun on my roof with pipes running through them, in the pipes will be oil ( I haven't decided what type of oil yet, maybe you could give me an idea ).
- I'm going to install a control system ( maybe reliable controls ) to control the output oil temperature to 390 Deg. C.
- The oil will go down to a room with a very large cylindrical cement casing, covered in insulation. In the cement structure will be sand or salt ( the cheaper one of the two ), the oil will discharge it's heat into the sand or salt.
- That heat will be extracted later when needed for in floor heating, DHW (Domestic hot water) heating, heat pump loop heating and electricity. Therefore this mass has to be big.
- Extracting heat for in floor heating, DHW, and the heat pump loop heating is straight forward, but for electricity it is not, as many of you may know, it is quite difficult to get electricity out of heat with a cheap method.
- Here is what I thought up, I would use thermoelectric modules. I'm looking to cover an area of 50 cm x 50 cm, with approximately 60-90 modules ( I would need the test the modules before buying them in large quantities). These modules will then be placed against a heat exchanger extracting heat from the sand and the opposite side of the module will be against a cooling side. The cooling side will be feed by glycol from stored cooling provided by the PV solar. I will incase them in a container and create a vacuum to avoid too much heat leakage.
PROS and CONS
PROS
- Safe
- Most simple in design
- Most inexpensive storage to all the other systems out there
- Less parts
- Less parts to wear, corrode, or fail.
CONS
- Inefficient electrical use
- I don't know the breakdown of oil, but it may need to be changed after a few years.
That is my idea of the system I'm going to build, I have looked thoroughly at HHO storage, H2/O2 storage, flywheel storage, battery storage, molten salt storage, kinetic water storage, use of a stirling motor and kinetic storage in general. Most of these ideas are very expensive in the long run and have to many parts involved. I wanted to simplify the system as much as possible and keep it cost effective.
When I build the system (maybe in 2 years time, I need to design the house around this) I will definitely post everything I'm doing on youtube for everyone in the world to use it, if it is feasible.
Let me know what you think
Mechster
In order to store thermal energy, you want to be able to isolate all conduction and radiation paths as much as possible. Vacuum is the best insulator, air is next. Silvered glass is an excellent reflector. This is why water heaters are built the way that they are. 390C is pretty hot. Are you going that high in order to try and reduce your thermal storage mass? How much energy do you want to store?
If you want simple, then store at under 100C using conventional water heater tanks. The main disadvantage is the volume you will need.
Wow, thank you guys for your information. Thank you, I really do appreciate your responses.
I was run out of another large solar forum by Harassment from the members for mentioning any new ideas.
MarkE - You're right, I was way out of my league thinking I could handle 390 C, it would be unsafe to be handling that kind of temperature for anyone starting this kind of stuff. I thought maybe 150 C of water in a pressurized water tank would be ok, but I looked at pressurized water tanks (because water is the best for storing energy), but they are very expensive. Almost $ 5k for a 400 gallon tank, 2 of them would achieve the same capacity at a huge bed of sand, but that's a huge price tag.
PeterK - I love your idea, I'm lucky where I live on a Island in Korea where they have a lot of Basalt Rock in supply.
Density Heat C Energy Density
kg/m3 kJ/kg K kJ/m3 K
water 1000 4190 4190
Sand 1682 830 1396.06
Basalt Rock 3000 840 2520
Granite 2700 790 2133
I don't know if my calculations are spot on, but the energy density of basalt rock seems pretty good. I really like the idea of a Heliostats, as it kind of looks like an ornament.
Do you think the modular heliostat would take up less space? My last question, how did you move the air through the system at high temperatures.
Thank you again, I'm going to do some more research on heliostats. This would be a cool build
http://energy.gov/sites/prod/files/2014/02/f7/csp_review_meeting_042513_kutscher.pdf
Mechster
Leakage is a big issue. If you go with storing in rock, then you will need to come up with a vessel design of your own that has really low leakage. That's maybe good if you want to experiment. water heaters work really well as long as you hold the temperature below boiling which you can manage with a bypass around your outside source to storage heat exchanger. There is lots of kit for this sort of stuff that is well proven.
Thermo electric may sound appealing until you look at the cost per Watt and the need to keep 300C material around to have any efficiency at all. As much as I hate to say it, but a NG fired generator is the cleanest night time solution. A high quality Diesel would be the next choice.
Combing the forces is giving the most, just like in nature:
http://energy.gov/eere/articles/making-algal-biofuel-production-more-efficient-less-expensive
mechster your original concept of 390 C is in line with what I'm doing, it doesn't scare me like big expensive water tanks, it's twice as much temp as a regular kitchen oven making diner & you see how little insulation they use. As far as space, solar energy is real but low density so the larger area you gather the energy with smaller managable Heliostats by one person, the overall size can expand as time permits.
To circulate the Hot air is just a fan, this could range from a Turbo salvaged from a car or most likely say a 6" steel pipe with elbow. drill a hole in elbow to clear a shaft with bearings outside, the shaft has steel fan blade in pipe, motor with bearings kept cool outside. the hole for the shaft is on the low pressure side of the fan so no hot air will leak out.
You could add a fan speed control with temp difference from heat exchanger to storage.
Peter
Peter K
Thank you for your informative post. You're making me want to go and set this in motion today! I already sketched the whole thing out and sized the bed, but I'm actually in the process of designing a house, so I'm looking ahead to projects I'll be doing and making space for them. Once I get stuck on something, it's tough to back off and finish up the house design.
That fan placement would be perfect, do you have it placed just before the manifold?
I also was thinking I could use a car radiator to capture the heat when I need it for heating the domestic hot water heater. And later on I'll expand the storage to maybe be used for the in floor heating in the entire house. The coldest it gets on the Island is -2, so maybe it is doable.
Hope I'm not taking up your time.
There is actually an informative review that I read about PCM's (phase change materials), I'm thinking of using them for my DHW storage and in floor heating storage. They apparently can hold 8 times more energy storage than that of water. That would cut my storage tanks down to about 1/4 of the size I need and maintain a constant temperature.
Here is the review http://www.academia.edu/4688840/Review_on_thermal_energy_storage_with_phase_change_materials_and_applications
Thanks Again
Mechster
PCM salts have been used sucessfully mostly in Europe. They are a bit expensive, and you need to make a design choice:
Use the salts with a pair of heat exchangers or only one. The latter route is simpler, but is best suited when you want the room temperature to be close to the phase change temperature. That works best when you are only trying to go one direction: Provide winter heating or summer cooling. The phase change temperature that is desirable in each situation is different.
Latent heat storage : http://www.wuerzburg.ihk.de/fileadmin/user_upload/pdf/Innovation_Umwelt/Vortraege/Dr._Hauer-Thermische_Energiespeicher.pdf (http://www.wuerzburg.ihk.de/fileadmin/user_upload/pdf/Innovation_Umwelt/Vortraege/Dr._Hauer-Thermische_Energiespeicher.pdf)
This kind of energy storage is really expensive !
Ideal solar building architecture: Sokrates, passive house http://www.dennisrhollowayarchitect.com/gifs/SunTempered/MethodologyDesign/SocratesZenophon.jpg (http://www.dennisrhollowayarchitect.com/gifs/SunTempered/MethodologyDesign/SocratesZenophon.jpg)
low energy architecture : http://www.building.co.uk/dazzling-achievement/3088489.article (http://www.building.co.uk/dazzling-achievement/3088489.article)
St.George school , Wallasay
House tect with black colored,metal particles mixed, zement plates/panels inert a tube net
Less expensive solar heat storage : Trombe-wall (ANWAR,France)
https://www.google.de/search?q=trombe+wall+architecture&biw=1024&bih=612&tbm=isch&tbo=u&source=univ&sa=X&ei=T8AMVKS6JcrE7AbDt4DQDA&ved=0CCAQsAQ (https://www.google.de/search?q=trombe+wall+architecture&biw=1024&bih=612&tbm=isch&tbo=u&source=univ&sa=X&ei=T8AMVKS6JcrE7AbDt4DQDA&ved=0CCAQsAQ)
http://www.pinterest.com/pin/147070744054553395/ (http://www.pinterest.com/pin/147070744054553395/)
Solar air heating collectors ( f.e. TM "Sunmate" )
and as ambiental energy collector heat pump :
Jacques Bernier AXERGIE https://web.archive.org/web/20110827103139/http://www.larbombas.pt/ (https://web.archive.org/web/20110827103139/http://www.larbombas.pt/)
("open source" technology, Pat. from 1987)
floor radiant heat panel : http://www.radia-therm.de (http://www.radia-therm.de)
Sincerely
OCWL
mechster like you I also decided to build my house with Solar in mind, not finished ! however we live here in a Round, 7,000 sq ft house. The center tower is cast concrete 6 ft ID * 8 ft OD * 34 ft tall, the bottom 12 ft are for heat storage, with 1 ft insulation 4 ft OD * 10 ft tall, this is for the rocks " not in yet " . My main focus now is to set up small scale Mfg of the Solar Heliostats
" Sunflowers " the task is to make high reduction gear drives for each axis, for the first 20 Prototypes I made double worm drives for each axis so that's 800-1 reduction, the little stepper motors " so far " have no trouble with the load & only step aprox 1 per min.
I think of a radiator " size " heat exchanger @ the focal but for air @ higher temp.
Other heat loads like water, floor heating, electricity & lets not forget food cooking, can all be done with raw heat, so if space is not the problem I would go with the most readily available IE cheapest " Hot Rocks " no maintenance, no leak, with this you can have solar cooking @ night.
still getting a " RoundTuit "
Peter
Peter K,
What is you're e-mail, I'll send you what I have drawn up. It's simple except for one feature to seal the entire system when not in use. I read in a few research papers that the main reason these systems don't work is because of the heat losses. I designed it around that aspect.
Mechster
mechster I don't think of the system ever being off except in failure, & it must be default safe.
there is no perfect insulation so on the outside of insulated storage is another space for air input into the system IE cold air return, lost heat is captured & directed as needed.
Solar looks to me like a half wave rectified power supply & we need sufficient " Capacity " to allow for missing pulses. You will likely want to direct the heat, need actuators, could be for vents or valves, repurposed windshield wiper motors if your handy. peter " at " microtrendrobotics " dot " ca
Peter
pump water uphill to a holding pond. Any rain fall and you get a little bit more solar energy input.
Quote from: sparks on September 08, 2014, 01:40:07 PM
pump water uphill to a holding pond. Any rain fall and you get a little bit more solar energy input.
It takes a big pond and substantial elevation to do much good. Say that you want to store one therm for overnight heating. That's 29.3kWh = 105E6J. At 9.8J/kg/m and 1kg/l for water, you'll need to lift about 10,000,000 liters*meters. So if your pond is shallow but 4m above grade, then it will have to hold 2.5m liters, the volume of an Olympic size swimming pool. If you heat water from 25C to 99C and store that, then going down to a comfortable 20C, you get 79C * 4.18E3J/l = 330E3 J/l, and 105E6J requires 317 liters, or about 75 gallons, within the range of a large water heater, or two small water heaters.
Mark,
Yes, that would be one big pond! haha I looked at flywheels, hydrogen, weights, water and a few others I can't think of right now for storing energy. $ per watt, it's tough to find something. Sun seems the best solution, if you could make a storage that would last 3 or 4 days without sun, it would be perfect.
Mechster
Considering that the "average" home in the U.S. consumes 18.1 kwh of electricity per day, one might investigate the use of gravity as a simple means of storing solar energy. Here is one example:
http://deciwatt.org/
It may prove an interesting exercise to calculate the increase in scale required to couple such a system to one's solar situation. Many solar users employ two battery banks so that one is charging while the other is being used. One of the cool things about a gravity system is that the full solar input can go directly to a motor which drives the lift pulley. Variable load parameters could also be met relatively inexpensively as well. Such a system could be quite hardy, avoiding many of the pitfalls of expensive and sensitive electronics, with many creative options. For instance, when one's expensive and heavy lead acid battery bank has worn out, one can employ it as the weight source....lol.
Of course, if one is in an area where solar is problematic, but wind is fairly constant, a PMA generator wind turbine setup could be coupled directly to a very efficient and simple gravity PE storage setup.
https://www.youtube.com/watch?v=HP3aAa_w2S4
Quote from: TechStuf on September 09, 2014, 05:48:16 PM
Considering that the "average" home in the U.S. consumes 18.1 kwh of electricity per day, one might investigate the use of gravity as a simple means of storing solar energy. Here is one example:
http://deciwatt.org/
It may prove an interesting exercise to calculate the increase in scale required to couple such a system to one's solar situation. Many solar users employ two battery banks so that one is charging while the other is being used. One of the cool things about a gravity system is that the full solar input can go directly to a motor which drives the lift pulley. Variable load parameters could also be met relatively inexpensively as well. Such a system could be quite hardy, avoiding many of the pitfalls of expensive and sensitive electronics, with many creative options. For instance, when one's expensive and heavy lead acid battery bank has worn out, one can employ it as the weight source....lol.
Of course, if one is in an area where solar is problematic, but wind is fairly constant, a PMA generator wind turbine setup could be coupled directly to a very efficient and simple gravity PE storage setup.
https://www.youtube.com/watch?v=HP3aAa_w2S4
See the post above. 18.1kWh or roughly 65MJ, translates to about 6.6 million kilogram meters of mass * height product. Don't get me wrong: For those who have the real estate, and a water supply to replenish evaporation and leakage losses, pumped hydro is about the cheapest way to store energy. It's just that the real estate and water are not available to most.