High Mass Solar Storage

Bob Gagnon plumbing and heating

Solar Space Heating

Use the home for BTU storage. A superinsulated home will stay warm for a long time especially if you have some passive. Then go to the tank when it is cloudy for a couple of days or so. Then when you run out of stored heat go to backup, Boiler- wood stove or pellet stove. Even in my poorly insulated house I get most of my heating on 40 or 50 degree sunny days by running the low temperature solar water through my radiant system. A small radiant panel to deliver the energy, and a couple more collectors, and you will collect more low temperature BTU'S in the winter, it won't cost that much more. Where I live solar space heating makes more sense, we heat for 6 months and cool for 2 or 3 weeks.

Thanks, Bob Gagnon

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scott markle_2

The problem I see is that the highest thermal loads are at night, when there is very little need for electricity, both on site or on the on the grid.

These systems would not make sense economically if you could not sell this unneeded electricity back to the power company (at retail price) while you are capitalizing on the thermal component. Basically (at night) your generating electricity that's not going to do any work (and getting paid for it). If electric cars (night time charging )enter this equation then the idea deserves consideration in heating climates.

If we are using the waste heat there is no question that these units are very efficient. As far as efficiency (without the heat recovery) the laws of physics (carnot cycle) limit the theoretical efficiency of a heat engine to 73%

"For example, a typical gasoline automobile engine operates at around 25% thermal efficiency, and a large coal-fueled electrical generating plant peaks at about 46%. The largest diesel engine in the world peaks at 51.7%. In a combined cycle plant, thermal efficiencies are approaching 60%.[2]"

for more details- http://en.wikipedia.org/wiki/Thermal_efficiency

follow the link to the 51% diesel engine it's staggeringly large, these are literaly the "engines of globalization".

As good at honda is at making efficient small engines It's probably not getting anywhere near the 51% mark. We also have to look at the embodied energy and the mechanical limitations of a reciprocating engine.

I'm not a big supporter of using natural gas for power generation, but the reality is that unless your using every bit of that waste heat your MCHP system falls way short of the best combined cycle plants, even with line losse which average 3-4% .

I think the only reason this kind of idea has any traction is because it can eliminate the need to build more plants to cover peek demand periods. If these MCHP systems were connected (smart grid) they could come on line at times of high demand and it would be worth it for the utilities to pay a premium for this power to avoid the cost of added generating capacity. I think we need to be planing serious reductions in our electrical consumption not working on ways to accommodate growth.

Mark Biro

Calling it high mass does not make it HIGH mass

I think Andrew's got it.

My best friend built a house in the last 1970s (in St. Paul), with solar collectors and a huge amnt of fist-sized rocks under the garage for seasonal heat storage. Lots of storage, lots of mass, lots of insulation, lots of calculations...

It did not live up to expectations, because it also had lots of complexity (e.g. air handlers), elec. energy use (again, air handler), heat loss, and initial expense.

I conclude: try almost anything else first. KISS. ;-)

Now, pha$e-change material$ could give great seasonal storage, but unfortunately, the cheap material, like ice (cut from lakes, eh?, and put in ice houses) is not what you are looking for. ;-)

k_2

re Scott

If I understand correctly, your definition of thermal efficiency is turning the fuel into rotational motion, of which IC engines are very bad. As I read the wiki article it mentions waste heat, so I believe that if you could run a diesel as a boiler, and load it's generator output to resistors also heating the water, waste would be minimal. when was the last time you had to clean the exhaust of your diesel truck? They burn cleaner in steady state than an oil boiler, I think, and there are few hills in the basement

A tiny diesel would be all that was needed.

drawbacks: maintenance, noise.