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Solar-Hydrogen Home "Furnace"

 
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jabailo



Joined: 20 Mar 2006
Posts: 1272
Location: Kent (East Hill), WA

PostPosted: Thu Sep 08, 2011 8:59 pm    Post subject: Solar-Hydrogen Home "Furnace" Reply with quote

ZEEP24 powers your house with hydrogen produced using solar power
Quote:

The ZEEP24 is capable of storing 1,500 litres of hydrogen at full capacity, which translates to around 5kWh of electricity. In terms of water usage, it takes 500 cc to produce 500 litres of hydrogen. The example FC-R&D give is 1.5kWh of energy giving you 100 watts of power for 10 hours. Thatís enough to keep the lights on at least. So, even if the fuel cells containing the hydrogen arenít filled to capacity each day, thereís still going to be a decent amount of free electricity to use each night. Or, the energy can not be used and continued to be stored until it is required. The beauty of the system is it continues to be of use even when the hydrogen fuel cells are full as the solar energy continues to be produced.


http://www.geek.com/articles/chips/zeep24-powers-your-house-with-hydrogen-produced-using-solar-power-2011098/

This article says, with full tanks, you have 5kWh of potential energy.

The average American home uses 908kWh per month according to USEIA (http://205.254.135.24/tools/faqs/faq.cfm?id=97&t=3)

That means 908/5 = 181 recharges...or 181/30 = 6 full charges a day.

So the critical question is how fast can the system recharge itself?

Obviously things like the size of the solar array, and the speed of their electrolysis system come into play...

One interesting thing to note...in the video from the article, they mention using solid storage tanks....rather than pressurized hydrogen. Wonder what material they are using...since that's a big research effort right now in American labs.
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brian-hansen
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Joined: 17 Mar 2006
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Location: Oregon

PostPosted: Fri Sep 09, 2011 1:44 pm    Post subject: Reply with quote

It is odd that you start with the storage capacity, and not the level of production, in your analysis. But maybe not so odd. I always find it promising when I'm given numbers to work with, in these articles, but I still often have problems given the vagueness of the reporting. Key elements are often left out, and we're left to making guesses as to what is really meant, and, subsequently, our interpretations become colored by our expectations and hopes at the outset.

Also, I don't do this every day, so I get rusty. How to convert between litres of hydrogen, kgs of hydrogen, kilowatt hours, and back again? I find myself not trusting the original r&d source link you provided. Not only is it translated by google from the original Japanese, but it contains contradictions directly relevant to your analysis. In particular, it claims that both 2000 and 4000 NL of hydrogen are the equivalent of 10 kwhs. So I'll leave those calculations aside until one of us establishes a reliable catalog of conversions (that also may include some accounting for the efficiency of the conversion, and whatever assumptions (temperature, pressure, etc) are germane.

So, anyway, I can understand why you went with the capacity question: Since you are going to essentially completely drain your storage 6 times per day, then you will need to have that much production capacity to keep filling it up. In this case, it is pretty clear to me that you can't. The reason is simple. If you assume equal energy usage throughout all 24 hours, then, by the figures you cite, you would use 30kwhs per 24 hours, and so, about 1.25kwhs per hour. A tank with a capacity of 5kwhs of energy would last only 4 hours before being depleted. If you used less energy at night, then I could imagine stretching that out somewhat. On the other hand, in the absence of googling it, I think there's some reason to believe that energy usage could be higher at night in a lot of instances. For the moment, I'd call it a wash, and note that this is a solar-based technology, which limits the hours of operation on a daily and seasonal basis, so the "sizing" of this system's storage capacity is insufficient for the application you describe (powering the average home).

Notice that I haven't said anything about the production. If it were sufficient, then you could just add more storage, and you'd be okay.

Like I say, I'd be interested in delving a bit more deeply into the production side (by first sorting out some agreed upon conversion factors), but so long as the author is leaving us guessing, and maybe making errors, or maybe including factors accounting for conversion inefficiency (1.5kwhs provides enough power to light a 100 watt lightbulb for 15 hours, not 10), I figure I'll make a guess of my own.

I'm guessing that the tank is sized for filling once per day, during the span of the daylight hours. Insolation varies between regions and seasons, but some rough calculations I recall for this region (Oregon) puts us at 4 hours of 100% solar input per day (you could think of this as the area under the curve of an average of "watts" per hour from the sun across all seasons and recorded for each hour). For some purposes, the maximum output of kwhs/hour is useful (it is the most impressive number). I just mentioned the average case. The minimum case would be most relevant when seeing whether the system was sized correctly, especially during the cloudy and rainy seasons. Anyway, basing a guess purely on the average Oregon day, I'd predict that the unit generates about 2Mwhs per year, roughly one-sixth of your goal. I guess you could just buy 6 of them, if all these guesses play out.
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jabailo



Joined: 20 Mar 2006
Posts: 1272
Location: Kent (East Hill), WA

PostPosted: Fri Sep 09, 2011 2:34 pm    Post subject: Reply with quote

Since one of my lifetime goals is to go off the energy grid, while remaining on the information grid, I have thought what about doing the math the other way around.

Specifically, given this device, what is the house I could build around it?

How big and how efficient would my house be so I could ideally have energy at all times....what level of appliances would I need. Could I build it so there is enough hydrogen left to power a fuel cell car.
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brian-hansen
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Joined: 17 Mar 2006
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PostPosted: Fri Sep 09, 2011 3:10 pm    Post subject: Reply with quote

Your goal can be a bit tricky because unless you have a backup system, you are limited by short dark winter days.

Solar PV is somewhat workable for this climate, for instance, but solar thermal (water heating) generally is not practical for 3-4 (or more) months per year. I would expect solar hydrogen to be more along the line of solar PV, which is good.

The typical way to get where you want to go is to first subtract heating and cooling needs (handle them separately), and then size the system, adding backup generators or other energy sources to balance out the dips you get from solar (so, geothermal, wind, microflow hydropower, and then conventional backup - gasoline, lp, etc).

Considering you are getting hydrogen, perhaps it makes less sense to remove heating from the equation, since it would seem to be pretty efficient at that.

Until we settle on some conversion / production rates for this technology (since I kinda don't believe the figures), I'll stick with my original estimate. When applied to my case, I've calculated that I use 5.5mwhs per year (not including heating). So, I might need 3 of these units. Getting my usage down is possible, but requires some lifestyle changes, and updated technologies and appliances. If I was out in the country, off the grid, then maybe it'd be okay only to take showers between 2-4pm, for peak solar thermal efficiency, and not so much in the winter. The question becomes, "how low can you go?" and what are you willing to do to get there?

In my understanding solar hydrogen behaves quite similarly to solar PV, even in areas where you might see some big difference. In particular, a hydrogen battery is fairly similar to an electron battery, and their efficiencies are comparable, overall.

We'll need some separate calculations to figure out how much hydrogen you need to drive the your car. How many miles? Miles per unit of hydrogen? For my case, I might need another unit to make auto fuel, along with a couple more (beyond the 3) to handle heating.

Again, working with a lot of guesses, it looks like I'd need to cut my overall energy use by 80-85% to be able to get by on just one of these units.
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jabailo



Joined: 20 Mar 2006
Posts: 1272
Location: Kent (East Hill), WA

PostPosted: Sun Sep 11, 2011 8:13 am    Post subject: Reply with quote

Looking back at my last electricity bills for my two bedroom apartment, which has all electric heat and cooking, as well as a portable air conditioner and several computers:

Statement Month Electric Usage (kWh)

Aug 429
Jul 326
Jun 505
May 546
Apr 692
Mar 736
Feb 1094
Jan 847
Dec 795
Nov 964
Oct 636
Sep 456
Aug 407

So an average of 650 kWh, but again, this is for all energy needs.

My two bedroom apartment is about the size (850 sq. ft) that I would be satisfied with in my off-grid design...so I would need to come up with that much electricity to run my life. I could probably cut down some things, like the size of my refrigerator, and the number of computers as well as doing away with the A/C (which I only run about 15 days a year...at maximum).

Quote:
In particular, a hydrogen battery is fairly similar to an electron battery, and their efficiencies are comparable, overall.


One difference is in lossiness. A typical battery will lose energy even if not in use...whereas a hydrogen tank will not lose any energy while in storage.

On the other hand, there is the cost of electrolysis as opposed to pumping the energy directly into a chemical battery's electrolytes. That's something I'll have to research.
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brian-hansen
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PostPosted: Sun Sep 11, 2011 8:40 am    Post subject: Reply with quote

Your figure of 650 kwh/month gives an annual usage of about 7.9 Mwhs/year. Following my earlier reasoning, that would require 4 of these units, or, alternately, you'd need to cut your energy usage by 75% to run your house on one unit. If you also wanted to run your car, well then, you'd need to cut more.

I note that, like most people, your energy usage is highest in the winter, which is a problem for the solar electrolysis approach. You would either need to upsize your unit significantly, add massive storage, or have winter backups.

So far as batteries go, electrolysis is reported to be fairly inefficient, though new technologies might improve that. For hydrogen, there is also a big loss from compression, which this unit appears to do. I've seen some mentions of seemingly bypassing some of the overhead associated with compression by performing chemical reactions to bind the hydrogen into more compact forms, but it is hard to shake the idea that these will also have costs in terms of making the reactions go both ways.

I notice that loss of (hydrogen) charge is also an issue unless great care is made in the containment. Hydrogen, I read, is so small that it infiltrates many materials, escaping, or making them brittle. Meanwhile, the loss of charge in an electro-chemical battery is relatively small, so long as you are not planning long term storage. Less than 5% per day if I recall correctly.

There are differences between these two kinds of batteries, and the differences might be important, depending on the application, but they also might not, and overall, they are roughly comparable.
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jabailo



Joined: 20 Mar 2006
Posts: 1272
Location: Kent (East Hill), WA

PostPosted: Sun Sep 11, 2011 8:51 am    Post subject: Reply with quote

Quote:
For hydrogen, there is also a big loss from compression, which this unit appears to do.


In the video within the linked article he mentions they use solid storage...but that's the only mention. Going from compression to solid storage at low temperature is the next step for hydrogen.

<b>McPhy's Solid Hydrogen Solution Chosen for Wind/Solar Energy Storage in Nottingham University's "Creative Energy Homes" Project</b>

Quote:
To respond to this challenge, this new phase of the CEH project is building a microgrid that will provide an energy management system across several houses. The project will investigate the optimum performance for storing surplus energy as solid hydrogen in McPhy Energy's MCP-N-4, a magnesium hydride (MgH2)-based storage tank, within the microgrid. The hydrogen will then be used to feed the fuel cells on an as-needed basis.


http://www.sacbee.com/2011/09/04/3885444/mcphys-solid-hydrogen-solution.html

I guess I could just go live there!!
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