SHPEGS — DIY Solar/Geothermal Electricity

rohar writes "SHPEGS is an open design not-for-profit project to design and prototype a base-load renewable electrical generation system suitable for moderate climates and built from common materials. The design centers around creating a local geothermal source with an efficient solar thermal water heater system and can be scaled from single residence to mega-scale. The heliostat system used in Europe's first solar thermal plant could be used in a scaled-down SHPEGS system with Practical Solar's small scale heliostats."

Comments

Dupe

[baptiste]

Isn't this just the Energytower renamed?

Re:Dupe

[thedarknite]

Yep, it actually mentions that fact in the interview bit near the end of the article

Re:Dupe

[weighn]

Isn't this just the Energytower renamed?

renamed, but the original article was based around the premise of a discussion into whether or not it would work.

The SHPEGS (Shit-Hot Power or Electricity Generation System) project "just works".

Goes well with a biothermal heat retention device

[Anonymous Coward]

It's called a "sweater".

IANAS, but...

[glittalogik]

Quick glance at TFA, sounds pretty straightforward. I wonder how long it's going to be before we start seeing community funded small-town plants like this in operation. Especially in America, it sounds like the energy giants over there are either going to collapse under their own weight or disappear up their own assholes, can't be sure which yet.

Efficiency?

[mdsolar]

I read though the site and found many calculations but I'm trying to figure out the actual efficiency of converting solar energy to electricity. I don't mind if the hot water out gets counted at 100% but I'm guessing that per unit area this does not do as well as silicon PV at 15%. If there is a table that gives this kind of comparison, can someone please point it out? Thanks.
--
Rent solar power: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

Re:Efficiency?

[rohar]

Solar PV is a different system. The SHPEGS design focus is base load electricity, cheap collectors and enhancing the solar thermal output with additional ambient heat from the air which will mean the collectors scale in a non-linear fashion. There is also a prevailing wind enhancement potential with the convection tower. I would think that both for simplicity and summer daytime operation in arid locations that Solar PV or a classic Solar Thermal system would be a better solution for output/m2 of collector. At night or for most of the winter in Canada, Solar PV has little or no output and there isn't a comparison between systems.

Re:Efficiency?

[NixieBunny]

Efficency can take a second seat to low cost and ease of producing the equipment. Where I live, in Tucson AZ, there's enough solar power hitting my roof to power the whole block's houses. I just couldn't afford that many PV cells.

I am interested in a system that can provide some relief from the cost of heating and cooling my home without a big outlay in high-tech stuff. This ammonia cycle is something that I was thinking of just a few weeks ago.. Perhaps if I was a thermodynamic engineer instead of electrical engineer, it would be second nature to me.

Re:Efficiency?

[mdsolar]

Thanks. I'm looking for a number though. For a solar tower you might expect 0.5% http://en.wikipedia.org/wiki/Solar_updraft_tower but this project is tweaked. If the heat is being stored, it is still solar power, but delta T may not be so favorable. For corn ethanol, the efficiency is about 0.06%. At this level of efficiency for energy production/storage competes with food production so it is not all that feasable. But, algae get close to PV efficiency http://mdsolar.blogspot.com/2007/02/photosynthesis .html. So, in terms of land use, I'm trying to figure out where this falls.

I wonder how this would be for growing winter crops as well: is the ground warmed eough? And, if it is, what kind of losses might be expected owing to water evaporation from soil?

Re:Efficiency?

[mdsolar]

Sorry, I replied to the wrong one. Can you skip down one? Thanks.

Re:Efficiency?

[mdsolar]

I replied incorrectly: You've got a pretty big roof if you can power the rest of the block. Many roofs have enough area to cover the power use in the home they cover, but not all. Probably most in Tucson. If you have Tucson Electric Power you can follow the links at http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html to get solar without the big upfront cost.

Re:Efficiency?

[rohar]

For a solar tower you..

Convection tower performance is very poor and the convection tower portion of the SHPEGS system accounts for less than 10% of the system output. It is still clean renewable power, but the convection tower wind turbine output is trivial. The chimney is there to allow a large volume of air to move across the heat exchangers efficiently and the wind turbine takes a slight advantage of the effect, but it isn't significant.

I wonder how this would be for growing winter crops as well

The thermal storage would be deep enough to not interact with the surface or shallow groundwater. The Drake Landing project has some information. This is another research document on thermal storage.

There is a lot of potential for integrating bio-methane which requires a very constant temperature as well as this Solar Hydrogen from methane production system. Algae farming also has a potential integration with the solar thermal storage.

Thanks. I'm looking for a number though.

I don't mean to avoid the efficiency question. Again, in an arid location with the majority of electrical usage for AC, Solar PV or Solar Thermal is simpler and probably more suitable. The cost/m2 of collectors is substantially cheaper in a thermal system, so I'm not sure what you are comparing. Marginal and poor land that isn't suitable for crop production or the roof of a Walmart isn't the cost factor, the solar collector is. The MIT group was able to get 1kW from 14m2 of trough collectors on a straight thermal system and the SHPEGS additions should improve on that.

There are also 2 heat sources in the SHPEGS system, solar and hot summer air along with two power generation systems, thermal and the wind turbine. In theory, the absorption system should improve not degrade the straight solar thermal system, so I would expect something better than 10% efficiency on the solar portion if you include the additional heat from the air. The conversion efficiency of the heat being extracted from the air is difficult to calculate. The energy cost is the energy going into the solution pump to pressurize the aqueous ammonia and there isn't the same direct cost in the volume of air being moved, in fact the more air that is moved the better the output of the wind turbine portion.

I used 5% thermal to electrical efficiency for the calculations to be conservative, and generally 10% is used for binary geothermal plants.

If you are comparing Solar PV, you need to account for battery cost and cut all the numbers by at least 50% to account for the daytime only output. Regardless of what is used for electrical storage, there are 3 months of the winter in Canada and the northern US where Solar PV isn't going to put out anything substantial and seasonal electrical storage isn't feasible.

The Toronto Exhibition Palace Live Solar PV Stats page has some historical data on Solar PV in winter in Canada.

Re:Efficiency?

[bussdriver]

I've been into this stuff for 15 years (hobby) and I've not made anything large scale (yet) as far as solar. The problem is that its of minimal benefit to me because I'm so far north and its cloudy.

What is best in any problem usually depends upon its end use (like playing computer games and getting yourself hacked are uses best suited for Windows.)

HEAT
If your goal is heat, which is the #1 energy load for MANY people, then its clear solar heat is more direct.
The KEY issue with ALL power systems is the conversion losses (which includes capturing.) Storage is the next big issue after conversion.

For heating, solar heat wins hands down by a large margin except perhaps if your on mars or something (where your air can turn liquid when its cold outside.)

COOL
Cooling is big if heating is not. A clever cooling system leverages the earth's 50F temp-- just running some garden hose underground and running water thru it and a car radiator and you are already in business.

Naturally the biggest deal with hot or cold is insulation and thermal mass, those are your first priority before anything else. You can work on that today and it will save you money. Your ceiling loses the most, followed by the walls and a close third is the windows and doors.

For cooling, I'm seeing solar heat based products that claim better than PV for the whole system. I've not seen a PV cooling system-- they just use the power on a normal unit. I don't know the numbers, not much interest-- a thermal syphon is plenty for me.

Electric Power

You can store heat better and cheaper than you can electricity, generally speaking.
PV is simple, direct but costly to setup and maintain (long term-- hopefully PV prices drop in the 30-40 years before panels need replacing.) The Heat to Electricity conversion process is complex and while it is good at large scales, I've not seen anybody with a small scale setup that is seriously being used. Also something people don't think about-- is the scattered indirect light which is more common in clouds and smog. PV will handle that better than the concentrating heat based systems (and they must concentrate to get high temp.)

Exposed concentrators (as opposed to infrared blocking coverings) will use the full-spectrum while PV doesn't use much of the spectrum-- which gives them a huge edge as well. The physics of the problem dictate that dumping spectrum means less power is possible (you could do 100% but if you skip half the light energy your only getting 100% of 50% = 50% tops.)

PV panels claim to last 30-40 years, which means payback in about 20. At that time their cost or performance will be higher. The problem with "payback" is that you are still paying for it so it is STILL costing you that much money which could be saved by getting something with a better cost performance ratio. It should always come down to lifetime performance cost-- a poor PV panel which costs nothing and lasts a long time can beat out "better" PV panel. Same for solar heat, Wind, etc. (or nuclear, which I've heard has never been profitable--its heavily subsidized.)

I've focused on insulation and heating. Those will not change much and are quite good TODAY and have low cost and quick 'payback'. Electricity is a secondary concern because its not my primary cost or environmental impact. Electric generation is still quite up in the air and costs will come down. Better thinking about a wind generator if you have some wind available; it could provide a better ratio for you.

So your question is not that important for people, and as far as the answer-- you will see PV power plants that are honestly profitable popping up as soon as they can beat the other methods. (I know canada is building the biggest PV plant, but I doubt its because PV won out... if it did, its solely from the cold temps and often indirect light which PV is unaffected by.)

Getting a Grid Tie is not cheap, but it beats wasting money on batteries. Never forget that cost-- if you are

Re:Efficiency?

[mdsolar]

Do you live in the southern hemisphere? In the north you want PV on the south side.

I agree with you that insulation is one of the best money investments most people can make it they have not already. Canadian building standards have really concentrated on this to great benefit.
--
In 41 US states you can rent grid-tied PV for what you already pay your utility: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html. Interstingly, the inverters are one per few panels and on the roof. This is done to help with modularity but now I wonder if many small inverters are cheaper than one big inverter. What drives the cost of the panels down is the scale of maunfacturing.

Re:Efficiency?

[mdsolar]

...seasonal electrical storage isn't feasible.

Thanks again for the reply. Things got tangled above. This kind of the point of the whole system. But, it is still putting out less power in the winter than in the summer whereas this may not match the power consumption profile. If PV is also used (because roof space is available) then the mismatch becomes larger. I wonder if shunting some ohmic heating of the thermal resevior might give a boost, especially to winter time delta T? With your pattern of heating this might fit well since you can protect a high temperature core by reducing conduction away from it. If this seems like it might be feasable, you might want to consider shaping the resevior even more so that it is somewhat spherical so that the volume-to-surface area ratio is maximized.

On algae, your suggestions seems like the third peice of the following puzzle: To get high production from algae, you want to have a concentrated source of CO2, protection against competition from less productive strains together with contol of water evaportation, and temperature control. For now, both the CO2 and the temperature control are envisioned to come from fossil fuel plants while greenhouses or clear tubes manage the other aspects http://mdsolar.blogspot.com/2007/02/photosynthesis .html. Klaus Lackner's CO2 separation from the air method http://www.sciencemuseum.org.uk/antenna/CO2hoover/ might replace the fossil fuel as a CO2 source, but it won't do the temperature control. Here, you might be able use only marginally warmed ground heat for this purpose from around the edges of the resevoir I think.

Re:Efficiency?

[Have Brain Will Rent]

I agree with you that insulation is one of the best money investments most people can make it they have not already. Canadian building standards have really concentrated on this to great benefit.

As long as you didn't live on the west coast where the application of building standards designed for the rest of Canada resulted in a billion dollars or more of damage to homes from water penetration, condensation etc. Most shocking was the later discovery that the government knew that such damage might occur and apparently hid the information.

Re:Efficiency?

[bussdriver]

No I'm in the north (brain fart?) and will be moving to Canada in the next few years. At that time I will build a garage & workshop which will act as a prototype to try out all these ideas I've been toying with. Then I'll probably build a green house before finally building a house. Yes, I do plan to live in the workshop.

Its fun to read about this stuff, but when you start seriously thinking of investing your own time and money into something you start to look deeper (that is, if you are wise with your money.)

Didn't think my post would be seen- almost didn't post. I'm not an expert in this area; (although, I'm surprised at what can pass as expert opinion in the USA.)

I'm weak in electronics; just starting to learn more of that. My current understanding is that its better to have one really good inverter than use many smaller, possibly lower grade ones. (If they are great, its likely they cost more and therefore you'd pay more to have one per panel.) Again, cost is a big influence in evaluating "was it worth it?" I'm not a movie star, so I can not afford to spend too much being 'green' just to feel smug. If I can find a good solution for myself it can work for other people as well.

It is easy to lose sight of the main goal. For CO2 people, and your big causes should be 1st. Your heating, car etc. You can boost millage just by driving "like a slow old person" and that doesn't cost you anything but maybe 1 minute of your time and less accidents (unless you drive as poorly as an old person. hey, accident rates are almost a bell curve and guess where the young and old drivers place..)

If interested in wind, hugh piggott has THE book on the topic and its rather hard to snag a copy of it; only ideas I have there are to try injection molding of blades with something that has a bit of flex and make a better generator (not pancake, but the typical cylindrical style with a slightly conical shape.)

Re:Efficiency?

[mdsolar]

You are probably right about the cost of inverters. The reason it is done with many in this case is that it simplifies installation, helps with shading and makes adjusting the system size easy. These are all plusses for making a rental business go where that systems may need to move from place to place more often than systems that are sold and part of the contract is to keep the systems tuned to the way people are using electricity. I think you'll see panel costs quite a bit lower by the time you are ready to build.

looks OK. one question bothers me...

[Ralph Spoilsport]

how can it separate the ammonia from the water without drastically reducing its ER/EI?

RS

Re:looks OK. one question bothers me...

[rohar]

It's fractional distillation and the heat is recovered from both the water and the ammonia. This is a good document on GAX Absorption Heat Pumps and the wikipedia Gas Absorption Refrigerator entry.

The step-by-step detail PDF outlines what is happening in the SHPEGS cycle along with the Flow Animation.

Ammonia/water is also not the only possible working pair, but it is commonly used in heat pumps and Industrial Heat Transformers and was used in the system to simplify explaining the concepts. A commercial absorption heat pump powered by a geothermal source with images and diagrams.

hold on

[mastershake_phd]

Whoa hold on there. Using geothermal power will speed up the cooling of the earths core. Once the center of the earth is cool the earths magnetic field protecting us from the suns dangerous radiation will disappear and well all die.

Re:hold on

[Kandenshi]

I'm pretty sure I already read about the effect that a planet's core cooling would have on/in Abarrach, the world of stone.

That book kind of creeped me out back when it first came out. I was a bit younger then though, and the rather violent necromancy used in the story was scaryish to a fragile young lad like myself.
I'll give you a hint, this book ends badly for many involved.

Damned entertaining though, and I avidly waited for the next book in the series.

Re:hold on

[Dunbal]

Using geothermal power will speed up the cooling of the earths core.

????????

      Seriously do you have any kind of idea of the amount of energy required to cause any sort of noticeable impact on the earth's core? It's like a colony of ants saying they will destroy all the buildings in Manhattan.

Re:hold on

[Anonymous Coward]

Seriously do you have any kind of idea of the amount of energy required to cause any sort of noticeable impact on the earth's core? It's like a colony of ants saying they will destroy all the buildings in Manhattan. The irony with this is that I'm sure thats what they said at the start of the industrial revolution about the air, now look at the mess we're in. If there is one thing you can count on us to achieve its the unthinkable...

Re:hold on

[dave420]

I'm not being rude, but is the answer anything like the answer to "do you have any kind of idea just how much oil there is"? I mean, ants COULD destroy all the buildings in Manhattan if the buildings weren't repaired and the ants had long enough.

Re:hold on

[Anonymous Coward]

I bet that's what everybody said about "climate change". How on earth can mankind affect the earth's temperature???

Joe

Re:hold on

[Dunbal]

I mean, ants COULD destroy all the buildings in Manhattan if the buildings weren't repaired and the ants had long enough.

      Unless of course people keep building. Do you have any idea why the earth's core is hot? Do you just think the earth is cooling, still, after a few billion years, and will continue to do so for another few billion? Do you think there are no GRAVITATIONAL FORCES from the Sun that actually knead the inside of the earth like dough, and THIS is what heats the core? The core will cool when the earth stops rotating. Period. Now, how will tapping geothermal energy stop the rotation of the Earth or reduce the sun's gravity, pray tell?

Re:hold on

[Abcd1234]

Umm... no... the Earth's core will cool when the residual heat from it's formation bleeds away, and the various radioactive elements that are responsible for heating it finish breaking down into lighter elements. Period.

Re:hold on

[Anonymous Coward]

The amount of heat energy can be estimated simply using some facts in the article: "... 600-700 kilometers below the surface - 2,500 degrees Celsius ..."

Radius of the earth: 6378km ... so let's assume the "core" had a radius of 5000km and a temperature of 2000C and is composed of Iron.

The volume of this sphere is 4/3*pi*r^3 = 5.2*10^20 m^3

The specific heat of lava is approx 4000 J/kg/C

The density of Iron is 7.86 g/cm^3 = 7860 kg/m^3

So by cooling off this ball of molten iron by 1 degree we would have access to (5.2*10^20 * 7860 * 4000 * 1) Joules of energy or 1.6 * 10^28 J (at 100% conversion rate).

Compare that to 3.9 × 10^22 J = energy in world's estimated total fossil fuel reserves (2003)
http://en.wikipedia.org/wiki/Orders_of_magnitude_( energy)

Re:Probably going to need active cooling

[Anonymous Coward]

You lost me there.

Arj

[adrianmonk]

Am I the only one who instantly thought of Arj Barker when reading that headline?

Too long to be shorts
Too short to be pants
Shpants!
ah-ah-ah
uh-ah-ah
oh-oh-oh

Yeah, I thought so...

Re:Arj

[eck011219]

Personally, I thought of SCMODS from the Blues Brothers (State County Municipal Offender Data System, I believe).

Likely not worth it...

[evilviper]

This sounds like it's going to be more of an investment than PV solar panels, and still not generate significant electricity.

Maybe it's not as much of an investment if you already have a well with significant ground water, but then you're likely spending a lot of energy just pumping it to the surface, from 30'/10m down to generate a small amount of electricity off of the temperature differential. If it's a shallow well, the temperature difference between the air and groundwater won't be as significant, so that's probably not an easy way to cheat either.

I imagine you're making the well or reservoir less valuable if you also want to use a ground-source heat-pump in the area, and save significantly on electricity/gas/oil. I'd certainly prefer an effective heatpump to (modest) electrical generation... Heating and cooling uses far more energy than anything else in my home. And a ground heatpump doesn't need massive solar panels in my yard in the summer months.

Re:Likely not worth it...

[rohar]

A lot of the SHPEGS system inspiration came from the Drake Landing Solar Community project which is a district heating system using solar thermal collectors on the garage roofs and borehole thermal storage for structure heating.

For colder locations, there is a lot of value in the structure heating component of the SHPEGS system.

Re:Likely not worth it...

[dbIII]

Photovoltaics are additive - double the area and you only get twice the power. Thermal solutions scale up. If you only look at the small scale it is not going to look very good.

Re:Likely not worth it...

[mdsolar]

It is true that heat retention improves with scale linearly and delta T can be increased with scale, but the cost goes up with volume (linear scale^3). One nice aspect of this system is that you might build it to last a few centuries in the below ground hardware so that the cost per unit time is low. It is difficult though to arrange multi-generational financing of this duration so the first users have to carry the install costs.

PV scales as you say, but the cost comes down a lot with large scale manufaturing, and the cradle-to-cradle-to-cradle aspects of recycling the PV look pretty positive so it carries reduced costs forward but in a way that spreads them without having to work out new finacial instruments.
--
Low risk finance: Rent solar power: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

I predict big problems already...

[agwis]

"The project is being managed with a similar methodology to Open Source Software Development and the ideas and contributions are being published openly on the Internet without an attempt to secure patents."

• little to none documentation
• support will most likely come through forums, mailing lists, and irc
• paid support contracts likely originate from knowledgeable engineers who live in exact opposite time zones
• frustration arising from having to download needed software through mirrors, but unable to find one that isn't down or broken
• disputes with lead engineers causing forks of the project. you will have to decide which path to follow
• nobody has put together a package for your distro, you have to resort to make, make install...never works
• eventually microsoft will announce that you are infringing upon 235 of their patents but they won't tell you which ones

All kidding aside, I will be watching this project. I keep hearing that if you can generate your own electricity and give back surplus to the grid then the power company has to pay you. I can't wait for the day I can call my utilities company and tell them they have 10 days to pay up or I will be forced to hand deliver a final notice!

Re:I predict big problems already...

[Anonymous Coward]

unfortunately, they'll just give you credit for that rainy month when you're not generating anything =/

Moderate Climates?

[weinrich]

If we are to believe even half of what Al Gore is spouting, the only moderate climates left on Earth in 20 years will be Chris Kringle's home town and some place in Northwestern Ontario.

Re:Moderate Climates?

[Dunbal]

If we are to believe even half of what Al Gore is spouting

      How could you NOT believe Al Gore? After all, he DID invent the internet!

Re:Moderate Climates?

[Anonymous Coward]

That's not as cool as Bush inventing how to do a kilo of coke out off the ass of a dead whore!

Re:Moderate Climates?

[Dunbal]

mods have no fucking sense of humor, as usual. Bleh, I'm a karma millionaire

Re:Wind turbine

[Miseph]

I still don't get the "why"?

Congratulations, you can insert Heroes (right? I don't watch the show myself, so I'm not sure) spoilers into an otherwise good post... so what?

Re:Wind turbine

[weighn]

Congratulations, you can insert Heroes (right? I don't watch the show myself, so I'm not sure) spoilers into an otherwise good post... so what? I don't watch it either but knowing that anyone is "killed permanently" is more of an assurance of a firmly based plot-line rather than a spoiler....unless her best-friend wakes up in ep.1 of the next series to discover that it was all a "terrible dream!".

Let's see a prototype

[Animats]

That thing has an incredibly complex cycle, with losses all along the chain. There's ammonia, water, steam, air, and hot oil involved, with heat exchangers all over the place. The paper attached to it doesn't describe the basic thermodynamics in any real detail. It's sort of like a solar-powered Rankin cycle system. But much more complex, and without solid justification for the extra complexity.

This might be credible if they had a working prototype, even a little one. A prototype in the 1 KW range would be about right. That's a backyard project. A 1KW plant would need about 10 square meters of collector mirror, which isn't too hard. Then they'd have something. All they have now is hype.

Re:Let's see a prototype

[rohar]

There are plans to prototype it, actually as soon as I finish coaching my kids softball. :)

Questions I am hoping the prototype will answer:

• The theory is that by using a Absorption Heat Transformer/heat pump to "upgrade" additional heat from the air, it will lower the amount of solar collector required for a given output and scale in a non-linear fashion. This adds a lot of complexity to a solar thermal system and although the absorption heat pump has been around for 100 years, it isn't that common of a technology and it's difficult to find experts in the area.
• By using the heat transformer concept, the temperature can be raised to use a water steam turbine as opposed to a lower temperature and a organic rankine system. Water is more dense than lower boiling point fluids and in theory the turbine power output is higher. The question is whether the power going into the solution pump to pressurize the aqueous ammonia to raise it's temperature that high justifies the increased power out.
• The negative buoyancy caused in the convection tower and it's fluid dynamics are difficult to model for someone that isn't a fluid dynamics engineer. In theory, the air intake of the tower can be orientated to prevailing winds, the heat exchangers can angle the air and a vortex can be created in the tower which will increase the angle of attack against the wind turbine. It's difficult to picture how this will work without a working prototype.
• A dozen other things.

As far as complex, the cycle isn't much more complex than an absorption refrigerator found in most RV's. I have one in my camper that is 30 years old, never been serviced and works fine.

Re:Let's see a prototype

[Anonymous Coward]

A 1KW plant would need about 10 square meters of collector mirror Considering a large majority of people don't live with spare land surrounding their homes 10 m^2 can become an issue in itself. Yes, the roof is the obvious solution but if you have skylights or aerials, possibly ordinances against additions on your roof, or just steep pitch that can limit if not eliminate the roof as a location.

and then are those of us who live in Seattle. What's this solar we hear about? Is it a new Toyota hybrid?

Re:Let's see a prototype

[Anonymous Coward]

I tried reading through your calculations and got a little confused. I was mostly looking at the "Hot" cycle, because that seems like the most useful (there's more hours of light during the summertime). It seemed like nearly all of the power calcs for the summer were related to the tower, and very little was used for the ammonia. Also because the ammonia needs a phase change and then to return to it's original liquid state, it seems it would add no energy to the machine. It fact because the phase change is a complete cycle using machines that are less then 100% efficient it seems using ammonia would reduce overall efficiency efficiency.

Most low delta-T systems are limited by Carnot efficiency which would be around 10% for 100 and 50 degrees F, and I didn't really see any high temperatures listed. You mentioned that the temperature difference between ground and air would be around 30 degrees C either summer or winter, which translates to around 10%. I realize that solar collectors will help improve the delta-T, but I didn't see anything about concentrated solar energy, so I assume that you are going for a low delta-T type of system. I could be wrong, but I think adding the ammonia to the system clouds the issue quite a bit, and you need a ton thermodynamic tables for ammonia and aqueous ammonia, before those issues will show up. Personally, I have looked into solar energy quite a bit, and have found that unless it's a PV system, or a concentrated solar system, it will not be very effective.

Having said that, your idea made me start to think (which can be dangerous). What are the possibilities of just using a bunch of mirrors focused on a black tower. There could be oil filled pipes on the tower (super heated for steam generation), and additionally you'd also get the wind generation. Obviously this isn't a generator for all climates, but it might be great for sunny climates.

Developing World Application

[FromTheHorizon]

I currently live in Indonesia, where people commonly burn rubbish - including farmers who burn the husks from rice production. Although this certainly isn't the most environmental form of waste management, I feel that if they are already burning rubbish, at least they could collect the energy from the burning?

Would it be possible to build a simple generator to convert the energy into electricity?

Re:Developing World Application

[rohar]

This is a very interesting project by a group of MIT grads that implemented a very cheap solar thermal system out of salvage automotive components (power steering pump, alternator, etc) for low cost deployment in developing countries.

The SHPEGS additions to this type of system (thermal storage, convection tower) could also be implemented cheaply from common materials and salvage parts.

Re:Developing World Application

[Anonymous Coward]

Perhaps a simple variation on a steam engine, driving turbines which could generate electricity through magnetic induction?

*reads article linked to by rohar*

That's even better! Using parabolic troughs (parabolic? Is there not a better name for them?) supplies virtually impact-free energy... water is probably not as effective as oil. It's a shame I don't live somewhere with more sunshine... (I'm at the south end of NZ.)

Re:Developing World Application

[khallow]

Another angle is thermoelectric generators. For example, here's some talk about a old Soviet design (from the Second World War) that could generate 2-4 W from a cooking fire or as in this case a kerosene lamp. I can't find it now, but there was a barrel shaped generator that could produce substantially more power. Gas or some other substance was burned in the lower portion of the barrel (which was slotted or holed so that air could come in from the bottom). The middle to upper portion was lined with thermocouples plates, and the top was either open or covered with a lid with huge air gaps (to keep water from entering via the top). I don't know how much it generated, but efficiency is typically 10% optimally (and this wasn't optimal) for these sorts of devices.

Re:Developing World Application

[Dan Ost]

Thermopiles are woefully inefficient. Much better to use that heat to drive a stirling engine connected to an alternator.

Straw bale as building materials

[Anonymous Coward]

I currently live in Indonesia, where people commonly burn rubbish - including farmers who burn the husks from rice production. Although this certainly isn't the most environmental form of waste management, I feel that if they are already burning rubbish, at least they could collect the energy from the burning?

The people who founded "Real Goods" (now renamed to Gaiam) http://www.gaiam.com/realgoods/ are involved in renewable energies and are big proponents of using straw bale (recycling the husks from crops including rice) as building insulation materials. Their non-profit arm at http://www.solarliving.org/ has books such as at http://www.solarliving.org/search.asp?keyword=stra w+bale&search.x=0&search.y=0 and also they have workshops http://www.solarliving.org/workshops/ , so they would probably be eager to talk with you and find out the situation in Indonesia.

You can also search on the Web for "straw bale building" and get some other resources.

So instead of burning as if it were rubbish, farmers could be possibly sell their rice husks as a useful form of building insulation, both for cold and hot weather. One man's trash is another man's treasure...?

In the future, the husks will hopefully also be useful in cellusoic ethanol production.

Thulsa Doom calls to you, infidel!

[Anonymous Coward]

"My child, you have come to me my son. For who now is your father if it is not me? I am the well spring, from which you flow. When I am gone, you will have never been. What would your world be, without me? My son."
                                                                                -Thulsa Doom
 
You have the great fortune of living within the divine grace of the great Thulsa Doom! You should get down on your fucking knees and pray for mercy. It is only by the power of Thulsa Doom that you are left to live and you should display this thanks to Him daily for sparing your pathetic life!
 
Don't get out of line, motherfucker, or you will face the wrath of Thulsa Doom and His loyal followers.
 
  Thulsa Doom!

Got it now

[mdsolar]

The Canadian system looks like it would be about 2% efficient. So, you'd want a collecting area perhaps 6 times larger that roof area of the homes served. So, if it served a town it would need about that much land again. The big plus is power storage so I wonder if it could be tweaked more to serve in the Winter and handle Summer/daytime with PV directly?

Can anyone help with the math?

[Bodhammer]

I recently read an article about solar power in Wired magazine: http://www.wired.com/wired/archive/13.07/solar.htm l

The article mentions a new design for a concentrator that only uses two motors. To quote the article -

"Then, in a weekend flash of inspiration, a young Caltech physics grad named Kevin Hickerson figured out how to reduce the number of motors needed to move 25 mirrors independently, a major cost factor. Instead of two motors for each mirror - the traditional approach - Hickerson's solution requires only two motors for any number of mirrors. The key is a mathematical curve known as the conchoid of Nicomedes (named for the ancient Greek mathematician, who discovered it). A grid of ball bearings arrayed to match the conchoid is attached to a frame inside the Sunflower. As the motors move the frame, the bearings control each mirror's position individually."

I have found this but it is not helping me much:

http://nvizx.typepad.com/nvizx_weblog/2005/08/conc hoid_of_nic.html

I have been unable to locate a more detailed explanation of the system and I'm not sure if this basic math is patentable. My advanced math skills are very rusty and I'm not quite sure where to start to understand this. I have an idea that this technique might be useful and I want to understand how to design such a frame. I did look at the concentrator page here: http://www.sandia.gov/pv/docs/PVFarraysConcentrato r_Collectors.htm but it was not much help.

These articles as well also have some implications for the benefits of a simple energy source:

http://science.slashdot.org/article.pl?sid=05/09/1 2/1621204&tid=126&tid=14

http://www.time.com/time/magazine/printout/0,8816, 1101299,00.html

Also, this today triggered my interest again:

http://www.renewableenergyaccess.com/rea/news/stor y?id=46765

I want to understand how to make a spreadsheet or something that would allow me to input number mirrors, focal length, size and it tell me shape, size a location of pivots. Can you explain it to someone who hasn't touched calculus in 18 years? I want to build a cheap one on my roof!

Re:Can anyone help with the math?

[vrmlguy]

Did you try Googling for any patents? http://www.google.com/patents?id=jI1-AAAAEBAJ&dq=7 156088

I bet these greenies got SCMODS ...

[ribman]

Jake: SCMODS?

Re:I bet these greenies got SCMODS ...

[ricosalomar]

State...County...Municipal...Offender...Data...Sys tem.
Cops CRT: <flash>APPREHEND IMMEDIATELY</flash>

First solar thermal plant in europe ???

[Anonymous Coward]

Not at all, from what I know, Themis solar thermal plant in the Pyrenées mountain build from 1979 à 1983 and operated from 1983 to 1986 might the first one (at least from what I know) : http://maps.google.com/maps?f=q&hl=fr&q=Targasonne ,france&sll=48.897851,2.16391&sspn=0.002998,0.0084 54&ie=UTF8&ll=42.502169,1.974776&spn=0.003362,0.00 8454&t=k&z=18&om=1 and

But this new one can be the first COMMERCIAL thermal plan in Europe (as said in the article) as the Themis was mainly for technology testing.

Is approximation leading the world those days ? ;-)

People just can't get enough of this Gore joke.

[skids]

...even though it's been prettythoroughly debunked. I wonder if it will ever wear off.

Are simple designs overlooked?

[Klaatu01]

Before I even visited the website associated with this article I imagined a more simple system for allowing the sun to heat water and create hydroelectric "spill" to spin small turbines. In a way similar to existing hot water heaters for mobile homes and powerless locations, a "closed loop" system with large, nearly flat bladders heated by the sun could increase a volume of water enough to spill it into drains. Each drain has an integrated impeller turning a small shaft connected to a generator and producing electricity.

Yes, the fabrication of these stand-alone systems would cost quite a bit of money at first, but there must be enough "engineering intelligence" available at this time to allow workable, extremely low maintenance designs to be created.

All to often it seem simple designs are overlooked in favor of large scale "plants" for generating electricity because we only have to build one (whoopie) and they employ local citizens providing economic support to the planet's community. We have been creating a system of dependencies instead of independent (distributed) solutions. It is old school thinking at its worst that is past due for retirement!

Also, I offer that the widely distributed power generating model is "insulated" against natural disasters and terrorism because if 20 to 70 percent of a "grid" is knocked offline, only that 20 to 70 percent is effected. In our current configuration one power plant taken out of service may leave millions in the dark and without support for their electronic gadgetry.

Has all this been mentioned before? Probably. But I feel the technical community-at-large has to continually raise its collective voice in favor of systems of updated design. American stockholders may take a hit by the loss of assest invested in decades old technology, but think of this in comparison to so called third-world countries leaping over "land line" phones and going directly to wireless! All of the money they save by NOT investing in wired communications infrastructure is being (or should be being) directed into lower cost, lower maintenance innovative new technologies delivering the same services.

Current power and communications systems should be kept as backups only and we as a nation should be encouraging people to get off the grid rather than plug into it.

Re:Are simple designs overlooked?

[FuzzyFox]

Water expands when heated?? News to me...

Re:People just can't point out enough...

[Anonymous Coward]

...that the joke has been "prettythoroughly" debunked. I wonder if they will ever just give up and realize some people think it's funny.

Hmm....

[Anonymous Coward]

Would it be a good idea to use an old town like Centralia,PA for something like this? Or would that just be considered coal power?

MODERATORS ON CRACK!!!!!

[mangu]

They gave (Score:4, Informative) to a comment that says:

The SHPEGS (Shit-Hot Power or Electricity Generation System) project "just works".

Informative? WTF??? How can you call informative a comment that says basically nothing and doesn't even inform the acronym right?

OTOH, another moderator gave to the first answer to that trollish comment a (Score:-1, Flamebait) because it gave information on some shortcomings of the SHPEGS concept.

Well, let's just hope I get some of those dumbasses in meta-moderation...

Re:MODERATORS ON CRACK!!!!!

[Anonymous Coward]

Yep that's right, today is (in all caps and with five excl. marks) MODERATOR CRACK DAY!!!!!

MOD PARENT INSIGHTFUL

[Anonymous Coward]

mangu said it. The quality of /. moderation has been getting progressively worse lately. I say we recycle the entire moderation system and start everyone anew.

People should have to earn moderation privileges.

Single motor

[mdsolar]

Here is a set of concentrators that run on a single motor. This might reduce PV cost by half though I'd worry about using this where there is snow and ice: http://www.technologyreview.com/Energy/18718/. This is coming to market this year. They are also working on a 2-D array.
--
Get afforadable solar power: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html

Oil...

[Stormmind]

I bet that's what they said about oil too...

Re:Wind turbine

[zippthorne]

Perhaps it's a sophisticated submission to the slashdot "turing test?"

It's Energy Innovations' Sunflower 250

[spage]

http://www.energyinnovations.com/sunflower250.html is the two-axis concentrator. It's a bit worrying that the website appears unchanged since 2006 and commercial trials were supposed to start in 2007. But supposedly Google's going with their subsidiary for a 1.6MW system.

Under Technology their web site describes all the approaches they considered and reluctantly abandoned. Very interesting read.