Solar Energy Survey

UPDATE!! Very simplified survey with far less questions and only check boxes (except for the country name)! very fast to fill! your help will be decisive for this project (if you have friends, you can tell them about this), and I will publish the results!

Here is also a petition to sign for the commercialisation of a small stirling engine vital for my project (I’ve contacted them for price ranges, no reply yet)

Hi, this is a friend of Farsthary.

I support (one of his sponsors) and help him manage the blog and I write from time to time documentation for you (cf. volumetric tutorial), and now he has exceptionally allowed me to use today his blog with many daily visitors because I need your help for a survey very important to me (I live in a small village, so I can hardly go and ask enough people in the street):

I am studying solar energy, and I have thought about a robust solar concentrator for household energy production: this will produce both heating and electricity, with temporary energy storage (a few hours) when the resource is not available anymore. The system will be secured and non-intrusive. This product will be easily removable (in case the house or the garden is not yours)

If you don’t mind, could you please take 2 mns to answer these questions as comments (just each letter with a few words)  and ask some friends about this, this would be a huge help for this project.

If you don’t have an answer for every question or if you don’t feel like typing, you can let some answers blank:  I’d rather have incomplete answers than no answers at all (moreover, the absence of answers at a question is also somehow an answer in a poll…)

1 ) country you live in?
2 ) very sunny? (you can also give an indication about the usual amount of cloudiness: every day, every weeks..)
3 ) available outdoor surface (square meters)
4 ) type: a) garden (%) b) roof (%)
5 ) how much of these surfaces are you ready to use for electric/heat production?
6 ) how do you roughly divide your energetic consumption between electronic devices, cooking and hot water?
7 ) peak consumption (kW)?
8 ) financing: a) you pay b) somebody else pay, but that person/establishment sells most of your electricity or consumes most of your heating during many years
9 ) how much of your energetic consumption do you want with renewable means (%)?
10) how much are you ready to pay for the product that suits your needs compared with standard photovoltaic panels for a similar electric consumption? (or how many years will you willingly let somebody else sell your electricity/heat?), the more the better your product is:
remember: this product will have differential advantage compared with photovoltaic, so even at the same price it cannot be put on a par
11 ) In case of the absence of the sun, how much time would you like the product to supply energy?
12 ) are your interested by an upgradeable, multipurpose product (water desalinization, organic waste valorization…)? you can give here your suggestions
13 ) how many people around you would you be interested by this kind of product according to you?
14 ) would you like to be contacted to be part of this adventure?

a BIG THANK in advance for those who will take some minutes to reply!  🙂

P.S: I will publish the results if I have enough feedbacks (about 50 answers in one month?)

Update (2 days later): the current participation rate is 0.3% (relative to the blog popularity), which is good if one considers that this article is out of subject.

Currently the user needs (big thank to those who have taken the time to reply!) and the possible characteristics of my idea relatively match (relative to the physical possibilities and prices ranges) but more answers are welcome to have statistics ideas!  🙂

Solar Energy Survey

25 thoughts on “Solar Energy Survey

  1. Willem says:

    1.Belgium; 2.rainy; 3.unlimited; 4.both; much as is esthetically viable (e.g. solar foil could cover the whole roofside facing the sun as opposed to solar panels); 6.workstations takes the bulk at 500W/h (1kW/h when rendering), freezer takes a lot; 7. 3kW/h; 8. I pay; 9. 100% if affordable; 10. depends on the sustainability/cost ratio. If it will work for +20 years, it can cost as much as 20000€ if it can deliver 15kW/h a day; 11. preferably 12 hours (wintertime); 12. yes, if affordable; 13. i’m usually the first to test it, so not many; 14. if affordable, yes.


  2. This sounds interesting. Could you give any more details about your project? What kind of technology does it use?

    I work for a firm that builds off-the-grid structures with solar and wind technology. I’d be interested to hear more…


  3. 1) Costa Rica
    2) 2-3 of 10 days are cloudy
    3) 15 square meters
    3) roof only
    5) all of it
    6) mostly computers, lights.. bit of water heater
    7) I have no idea
    8) I pay
    9) the more the merrier
    10) pay for what?
    11) a whole night
    12) not really
    13) ~3
    14) for sure


  4. Ruddy says:

    Hi ZanQdo, thanks for your replies! 🙂
    I have completed question #10: this is a relative price (gap in percent) relative to the photovoltaic solution (ex: 30% cheaper).


  5. Marcus says:

    0) Please more info: What are the advateges of your solution over others? Note that aestehtics are very important. A description or drawing of the thing would be good to decide if I would buy it.

    1 ) Southwest Germany
    2 ) Winter (October-February): cloudy 5 days of the week. Spring/Summer: Sunny 4-5 days of the week.
    3 ) 20m
    4 ) a 100%
    5 ) 6m2, if my wife let’s me 🙂 or more if the thing is removable when there is a garden party.
    6 ) don’t know
    7 ) –
    8 ) I pay.
    9 ) at least 50 percent, 80-100 percent would be nice if I had a roof.
    10) I would say 1000-3000 Euros if it is cost effetive.

    as I mentioned above, to me it’s not clear which is more effective and what photovoltaic does cost, how effevtive photovoltaic is and how much percent of Energy consumption a household can produce with say 10m2 of photovoltaic cells.

    11 ) 4-6 hours
    12 ) upgrade yes, multipurpose…well, not for me but perhaps you should built something in that gives husbands a good point to convince their wives. Like it makes a good smell or can give them hints what clothes to wear.

    13 ) 2-3
    14 ) YES!


  6. Chubaso says:

    1 ) Germany
    2 ) Usually not very sunny, the first months is just gray and rainy
    3 ) 0 – living in a house where there is no backyard, and i wont place any solar panels on the street where the kids are playing ;-), so the only way would be to place the panels on the roof (but this is in our case not accesable)
    4 ) see -> 3
    5 ) if i had this i would use the whole room, because green energy is always good!
    6 ) 45 40 15
    7 ) no idea at the moment, sorry dont have an answer to this one
    8 ) we divide the costs and everyone living here has to pay a part of the costs
    9 ) if possible 100% , but i realistically i think about 30% would be possible if there were big solar pannels on our roof
    10) Shouldnt green energy be cheaper over time ? (it comes from sun and the sun wont be exhausted so fast ;-))
    11 ) At least over night. But if its just an additional energy source to the common powerline, i think it does not really matter
    12 ) Yes i would be. Also i would suggest to use different green enrgy sources like thermal heat from the ground and wind energy. Why not combine all those different green energy sources to increase availabillity (for example if there is no sun there might be wind and so on)
    13 ) I dont know, but i think those old people living in our house too, wont be interested in fresh but also complicated ways of using green energy. Maybe you have to rely on the young people…
    14 ) Id like to watch the progress on this one, but i cannot decide to change the power supply in our multi family hose ^^ So id love to be connected to see the progress, but unfortunately i cannot use this green energy at the place iam currently living at.

    a big thank in advance for those who will take some minutes to reply! 🙂 – we have to thank people like you , because you make the use of new energy sources possible and save our planet !


    PS: Sorry for my bad english, if something isnt clear pls feel free to contact me


  7. Ruddy says:

    Hi Marcus, I’m the one who wrote this article

    if you want only electricty and don’t need energy storage (connection to the grid, and the operator buys your electricity), photovoltaic in 2-3 years (cheap chinese panels, projections give 1$ per Watt peak vs actual price: 4.5 $/watt peak) will be more interesting and simpler, provided that the petrol cost do not increase to much (photovoltaic production cost evenly depend on fossil fuel required for the purification of silica). Furthermore in very cloudy countries, standard photovoltaic panel are more interesting as they collect diffuse light, compared with solar concentrator who usually only collect direct light (cf. reflection).

    If you look for energy autonomy, my product will be more interesting as solar energy will be stored in a cheap and efficient way (refractories heated at 400-600°C as a storage) compared with batteries that you have to regularly replace. So this solves the problem of the transient solar resource. The solar to electricity yield should not be very high for the cheapest version (10% compared with 15% for photovoltaic), but this could be easily increased up to the 15-20% range with better (but a bit more expensive) materials for the generator (stirling engine)

    So even if the first version should be less efficient relative to electricity production for a given surface compared with photovoltaic, it will be much cheaper (components are basic, ten times cheaper then current photovoltaic for a similar electricity output, even more if mass-production), and will provide high temperature heat allowing future, optimized upgrades (the higher the temperature, the higher the theoretical heat-to-work (electricty) yield is), so a 15-20% yield is not unrealistic at all

    My product is not incompatible with photovoltaic, it can be complementary: the concentrator could be use with small, special photovoltaic panels to have a high power at a lower price (look for concentrated photovoltaic). It should be modular and tweakable so that the end user can adapt it to its needs.

    Finally, the energy not converted in electricty can be use for cooking and hot water. Thank to the high temperatures, you can directly generate hot water, you don’t need a big water balloon with its risks (legionella)); and you can do quick solar cooking.

    In any cases more precise choices on the design will depend on this poll, so do not hesitate to answer even if you hardly believe in its success.

    I am currently in the process of choosing the material and the standard dimensions for a prototype. The parameters will be chosen according to the poll results.



  8. Ruddy says:

    Marcus, Chubaso: Thanks for the replies! 🙂
    Marcus, I cannot give all the pictures yet (no protection at all at the moment, I would like to earn a living during a few years thank to this product, with an exception for developping countries (can copy it as long as they don’t use the electricty commercially). But the idea is not new: it uses a cheap reflective device to concentrate the sun inside a cavity made of refractory bricks that act as energy buffer. Heat will be then generate electricty via a stirling engine. All stuffs can be quickly mounted/unmount. (if you organize a garden parten).

    After the dimensionning I will do numerical simulations to check the behavior of such a system:
    – concentrating behavior under blender (raytracing) for different position
    – dynamic thermal behavior of the bricks (openfoam): loading during day (temperature increase), unload at night.

    Marcus: question 10: in Europe, you collect roughly at least 1000 kWh/m2/year of sun light (slightly more than 2000 kWh/m2/year in the sun belt), so with a 15% photovoltaic efficiency you collect 150 kW per square meter yearly. As a comparison, the average yearly electric consumption of a household in Europe is about 4400 kWh.

    Chubasao: also question 10: yeah, you’re right: the energy should be free after a few years (estimations: about 6 years before earning money compared with commercial electricity: 0.11€/kWh). Ideally, the system is simple enough so that people can built most of it from cheap parts.

    Regards and thank again for your interest!


  9. Ruddy says:

    Chubaso: relative to question 14, you are perfectly right: we must not be fanatic, but make use of every available energy sources. However, to begin with, it would be too complex to develop everything at once, so I focus first on solar concentrator, as according to my researches the concentrating device I’ve found is simple enough for a wide deployment, and is very robust and can be removed easily. But we could imagine organic wastes as heat booster, that you could put into the hot refractory cavity as an extra energy sources (though I think that using this as compost is better)


  10. Ruddy says:

    Marcus: as an indication, the product uses little materials (especially the concentrator) and the most impressive volume will be the receptor/stirling engine (like a petrol barrel for a model providing continuously hundreds of watts)).
    However we can find way to make it more discrete, but this would implies the use of a patented part, so slightly more expensive.


  11. farsthary says:

    1) Cuba
    2) yes, near every afternoon get cloudy and rain in summer, in winter is very dry and sunny
    3) 30 x 15 m are my backyard
    4) garden 50% roof 50 % (to build 😉 )
    5) all the roof
    6) winter (40, 40, 20) summer (50,50,0)
    7) I think 250 kw month? (I will check my electricity bill)
    8) I pay
    9) 100%
    10) I don’t have references to compare prices 😦
    11) the more, the better, probably the whole nigth till sun returns 🙂
    12) yes, if is multipurpose better
    13) here it will be a statal decition, probably for enterprises or rural houses or after hurricanes or natural dissasters
    14) yes 🙂


  12. 1. US
    2. Yes. Very humid as well. Maybe from around beginning of March to end of September it stays pretty much sunny.
    3. 100 m^2
    4. roof 80% — garden 20%
    5. probably 60% or so
    6. 30 30 30
    7. I’d have to look
    8. I pay
    9. 80-90%
    10. maybe $3000
    11. 16 hours
    12. don’t really know
    13. maybe 4 or 5 off the top of my head
    14. sure


  13. 1 ) Spain
    2 ) Aproximately 275 days of sun every year
    3 ) 1000m^2
    4 ) garden and roof
    5 ) 10% max.
    6 ) Cooking, hotwater, lights and TV
    7 ) 1,5KW
    8 ) financing: a) you pay
    9 ) 100%
    10) 5000€
    11 ) 24 hours… if its possible. I would like to have a normal refrigerator!
    12 ) Will be fine something related with organic decomposition to create biofuel 😛
    13 ) 200 aprox
    14 ) If its interesting, will be fine!


  14. Rhys says:

    1 ) Australia
    2 ) more sunny than not, 4-5 days sunny 2-3 days cloud (usually
    3 )roof is something like 200m2, not sure of the rest of the yard.
    4 )
    5 )we would use all the roof, AS LONG AS it doesnt effect the look of my house. Flat panels all over are good.Big pipes/tubes barrels etc not so good. If the latter is the case, it would be stuck where the solar water heater is (15% of the roof)
    6 )computers, tvs get used alot. Electronic water heater used when the sun has not heated it. Electronic oven used very often, but use gas cooktop.
    7 )not sure
    8 ) ourselves pay
    9)All of it eventually, wether it comes from giant solar panels/wind farm in the desert, or from my roof doesnt really matter.
    10)not sure how much these things cost.
    11 ) not sure
    12 )upgradeable is good
    13 )no idea
    14 ) not at this time


  15. Toon Scheur says:

    1) Bonaire
    2) What is this thing called cloud?? It is like 310 days sunny
    3) yard is 1001 m^2. Roof not sure. We have spanish tiles roof, so we won’t do anything on roof.
    4) At our current house the roof is like 40 m^2 and the garden is 1000 m^2. But shortly at our new home: garden is 1001 m^2 roof is like 360 m^2==> garden=60%, roof=30%
    5) 25 m^2 (5×5 meters)
    6) Electronic devices 100% (We have a gas stove and no heating=ice cold water)
    7) Peak compsuption? You mean at any given moment? … 2 kW on average if we are ironing clothes, the AC is on and the microwave is on for a duration of 10 minutes. If you mean monthly power compsuption: 130 Kwh I think.
    8) ( a)
    9) 100%!!! I desperately want to go off grid!
    10) For an off grid solution, I ready to pay up to $20.000
    11) 12 hours
    12) Yes!
    13) I know of 2, but being the tip of an Iceberg, I think there would be at least 20 people. Here the energy prices are the highest in the Caribbean region.
    14) Yes.
    A consumer alternative solution pays for itself. Compare it to a car, who will cost you only money the moment you buy it. There is no downside if you can replace your monthly energy bill with the loan payments for an off grid solution.


    1. Ruddy says:

      Hi Toon, thanks for thr replies! (also thank to the others!)
      2) yeah, this is only a very qualitative way for me to estimate the yearly insolation on a horizontal surface (1000 kWh/m2/y if very cloudy, 1500 otherwise (2000 kWh if sun belt and little cloud (texas, nevada)).
      7) yes, power in kW, I need it for an estimation of the electricity generator. For the electrical consumption (in kWh), I take values for a standard household (about 11 kWh of electricity daily). However, if the peak consumption is extremely high or if the user seems to have a lot of computers always set on (ex: render farms like Willem), I will roughly estimate the consumption (ex: 10 computers 24h/24h –> about 70 kWh daily)
      10) very realistic price: for such a price, you could produce more than several times your electricity provided the stirling engine is available (I won’t produce it, instead another firm)
      * 9000$ for the ST-5 stirling engine (3.7 kW, no production at the moment) extremely robust stirling engine (heat-to-thermal: about 10% , but cogeneration is very easy (desalinization?))
      This is an association (nothing to do with me, I am citing them as they can provide very robust and not-for-millionaries engines, and their history speaks for them)

      * my concentrator (still on the paper) in the giant version (but I prefer small units for convenience, so this is just an example) and 100% off-grid (assuming 1700 kWh/m2/year for Bonaire, a 60% solar-to-heat efficiency, this would require about 350 m2, so between $10.000 (six years warranty) and $25.000 (20 years warranty).

      So between $19,000 and $34,000 without mass-production (if mass-production, the price drop can be massive as little material and technology is required compared with concurrent systems, that’s why I need a good poll to discuss with partners and have an idea of the logistic…)
      Moreover, once the stirling engine is optimized (15-20% is very realistic, instead of 10%) the global product will be much more interesting!!! (surface- and price-wise)

      Electricy must be extremely expensive at your place! (this explains your low monthly consumption)

      regards and thanks again!


  16. Toon Scheur says:

    Hi, thank you for your reply. Our energy bill is on average $ 142. Since it is very hot in Bonaire, we have a couple of those industrial fans constantly on. And then there is the AC.
    The electrical bill is kind of funny because almost half of that is really a compensation for the fuel price fluctuation, and since its fluctuating upwards, it won’t matter if you have only you’re fridge on and a couple of energy saving lamps: the moment you start consuming energy here, you are paying a disproportional part due to those provisions.

    So, it is a sterling engine? That is like the ultimate can run on anything engine. I’ll get a bag of ice ready to make the heat differential higher 😉


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