Heat Harvester (Freewatt Cogeneration System)

GreenPowerManiac · December 2009

Another article caught my eye called the "Heat Harvester" from the Freewatt home heating system. It's supposed to harvest heat from generators and furnaces as a last vain attempt to re-use the heat power, I assume. Anyone heard of the stats for this one ?

Solar Guppy · December 2009

Re: Heat Harvester

GreenPowerManiac wrote: »

Another article caught my eye called the "Heat Harvester" from the Freewatt home heating system. It's supposed to harvest heat from generators and furnaces as a last vain attempt to re-use the heat power, I assume. Anyone heard of the stats for this one ?

Are you trying to make this a full time job for us hunting down all the BS, pie in the sky systems your dredging up?

There is nothing magical out there , just endless scammers looking to get your hard end monies

Cariboocoot · December 2009

Re: Heat Harvester

I don't know about this device specifically, but harvesting 'waste heat' in general is tricky. It's usually too low to be successfully captured and transfered as there are always losses with any process. To make something generic to capture heat from any generator you've got lying around seems very iffy.

But if you have a liquid-cooled generator then you have a potential for grabbing that heat from the cooling system in the same way as a car's heater works. Air-cooled is more difficult to work with, because of the need to isolate potentially harmful fumes (any method of doing so automatically introduces barriers to heat transfer as well).

I spent quite some time in my life dealing with waste heat from machinery. Either trying to get rid of it so the thing wouldn't over-heat in Summer or capture it so it wouldn't freeze solid in Winter. It's not as simple as it seems at first glance.

mike95490 · December 2009

Re: Heat Harvester

Aside from the product link being a "non-work safe side" and blocked by nanny-ware, the heat harvester is a shroud of some sort that goes over a Honda co-gen system
http://www.ecrinternational.com/products.asp?type=Freewatt

And the Honneywell wind gen scam is on the same handyman page of questionable do-dads.
http://www.handymanclub.com/club/default.aspx?top=37538&rt=37660

Next time, you post the links, I'm not searching for this ^*#@^*)# again

GreenPowerManiac · December 2009

Re: Heat Harvester

"But if you have a liquid-cooled generator then you have a potential for grabbing that heat from the cooling system in the same way as a car's heater works".

Sounds like a heat exchanger. I'd imagine that a LP gas generator is not very efficient, but the idea of utilizing heat from an electric producing resource is not unimaginable.

I had an option to put a residual heat exchanger into my existing furnace so when the thing fired up, it would also help heat the water in my radiant flooring system. However, it was indicated that was not available for my model. I've often thought of ways to push low volumes of air at the vent stack before it reaches the outdoors to capture the excess heat in the tubes.

hillbilly · December 2009

Re: Heat Harvester

I know no specifics regarding harvesting waste heat and turning that into usable energy, but I do know that there has been serious research into trying to capture the heat from automobiles. Sorry I don't have any of the details, but thought I'd mention that there is some real work being done in this area... I know that their aspirations were somewhat substantial regarding how much energy the felt they could capture. Haven't heard much from them about their research in a year or so now... so who knows where that technology stands...

GreenPowerManiac · December 2009

Re: Heat Harvester

Good point.

I'm thinking that you're referring to more of a heat pump system for air conditioning in an automobile, which is a great idea to put all that heat to good use and with little extra power consumption. Maybe a slightly higher pressure water pump would satisfy the needs of an "absorption chiller" type addition and eliminate the need for a compressor.

hillbilly · December 2009

Re: Heat Harvester

GreenPowerManiac wrote: »

Good point.

I'm thinking that you're referring to more of a heat pump system for air conditioning in an automobile, which is a great idea to put all that heat to good use and with little extra power consumption. Maybe a slightly higher pressure water pump would satisfy the needs of an "absorption chiller" type addition and eliminate the need for a compressor.

Actually that wasn't what I was referring to at all; friends of friends of mine had mentioned something more along the lines of capturing energy from the waste heat produced by a vehicle's engine. They felt there was a "substantial amount of energy" that could be captured, stored and later used. Sorry for the lack of details, it was a couple years ago they mentioned it in a brief conversation (most of the technical terms way over my head I might add).

GreenPowerManiac · December 2009

Re: Heat Harvester

Well, any kind of heat capture can be converted into energy. Things like the steam engine and pressurizing causes things to move.

Brock · December 2009

Re: Heat Harvester

I think this has come up here, that is a 12v battery charger that was run off the exhaust, I believe it was a pelter system and had an output of about 10 amps (I could be way off), the setup was really expensive, maybe $1000 and supposedly you could remove your alternator. They were having issues on cars that took shorter trips because there was no output until the system was really hot, and there were issues with it working in hotter climates with cars running AC (blower fan consuming 20a at 12vdc) along with the all electric radiator fans now also pulling 15 amps at 12vdc.

This is one of those situations that you could spend $1000 to save $100 in gas over the life of the car, that is, if it works.

BB. · December 2009

Re: Heat Harvester

But collecting heat from devices can have their own issues...

Problems with carbon monoxide like Marc said.
Issues with running motors too cool.
Issues with running exhaust stacks too cool (like wood stoves) causing creosote build up, messing up draft, and possible chimney fires.

Steam engine/wood fired boilers have always been a draw for the amateur mechanic. However, steam boiler explosions are not for the faint of heart.

Mythbusters has a few shows now showing what happens when a home water heater is overheated (~350+ PSI and Degrees F).

Mythbusters water heater (first show from a few years ago)
Small hobby boiler explosion video/thread
Norway Ship Boiler Explosion

-Bill

GreenPowerManiac · December 2009

Re: Heat Harvester

You never know, Toyota could add that to their Prius. Seems like they're adding up a bunch of small ticket items and making a big fuss about it.

The vent stack idea was more of a PVC series of smaller tubes to simulate a radiator element to capture some residual heat before it escapes to the outside. My LP water heater backup is one of those power vented type. It's a lot of wasted heat if you ask me.

icarus · December 2009

Re: Heat Harvester

Prius' already suffer from overcooling. Except in the HOTTEST climates, the grills need to be 75% plugged in order for the engine to get to proper temps. Cold climes 100% grill blocking is recommended. With out blocking the grill, you never get any heat to the heater, and the mileage takes a huge (25%_+) hit. http://priuschat.com/forums/search/search-id/1770390/

If you are interested.

Tony

BB. · December 2009

Re: Heat Harvester

If I recall correctly, the Prius also has a "thermos" storage system to try and get the engine up to temperature as soon as possible too. Obviously, reheating the thermos storage takes energy/time too.

-Bill

Cariboocoot · December 2009

Re: Heat Harvester

GreenPowerManiac wrote: »

"
I had an option to put a residual heat exchanger into my existing furnace so when the thing fired up, it would also help heat the water in my radiant flooring system. However, it was indicated that was not available for my model. I've often thought of ways to push low volumes of air at the vent stack before it reaches the outdoors to capture the excess heat in the tubes.

A word of warning about flu gas heat exchangers: it is possible to extract too much heat from flu gases, causing them to cool to the point where the chimney no longer drafts properly. You may notice quite some difference in recommended venting for standard vs. high efficiency furnaces. The latter have smaller vents which operate at higher velocity because the temperatures are lower (more of the heat goes into heating the inside rather than the outside). Canada is requiring only hi-efficiency furnaces be installed, new or retrofit, as of next year.

GreenPowerManiac · December 2009

Re: Heat Harvester

Does the Prius run PMAs for power production rather than the standard ?

What a power overload that could produce. Excess power could run a heating element to warm up both motors and a heat pump to cool it in Summer.

My furnace is high efficiency, Coot. It still gives off considerable heat through venting.

icarus · December 2009

Re: Heat Harvester

"Does the Prius run PMAs for power production rather than the standard ?"

What?

GreenPowerManiac · December 2009

Re: Heat Harvester

Replace a Standard alternator with a PMA alternator. Use the excess power to heat the combustion motor & D/C motor when cold. When warm could charge the batteries.

BB. · December 2009

Re: Heat Harvester

Permanent Magnet Alternators are--what? 10%-20% more efficient because they don't use DC current to generate the magnetic fields?

Not a huge increase in efficiency. I guess part of the issue becomes if it is a 100% current 100% of the time (like a wind turbine) or something that is modulated and runs at 100% very little of the time (alternator in a car).

Permanent Magnets seem to have their own issues with how they survive weather (I believe that the typical high filed PM's are very senitive to water based corrosion--so very sensitive to sealing/mounting.

Lots of tradeoffs in engineering and costing for high volume products (such as cars). I would guess that these automotive engineering teams have worked the numbers really hard already in their choices (usually with cost/profit being a huge driving force).

-Bill

Brock · December 2009

Re: Heat Harvester

Our VW diesel has the same problem with cold weather and mileage. The engine doesn't produce enough heat to keep it at the right operating temp and when it's not warm it is far less efficient. I did a test by preheating the engine coolant. If I preheated it on every trip to work (about 11 miles) I saw about a 5 mpg increase compared to not pre heating. (Yes I know the electrical energy offset the diesel consumed), but at least I had cabin heat on the way to work...

Don't get me started about trying to heat the cabin in cold weather, even with a 100% grill block...

In later version VW added a 1000w resistant element in the dash that was turned on when the coolant was below 120F, not only did you get some heat right away, it added load to the alternator and engine in turn heating the engine up faster.

Having an engine below normal operating temps the emissions suffered greatly as well. This is one of the reasons the Prius runs until it is “warmed up”.

baldy672 · December 2009

Re: Heat Harvester

GreenPowerManiac wrote: »

Another article caught my eye called the "Heat Harvester" from the Freewatt home heating system. It's supposed to harvest heat from generators and furnaces as a last vain attempt to re-use the heat power, I assume. Anyone heard of the stats for this one ?

The freewatt ("Heat Harvester" is apparently the catchy phrase that Handyman magazine made up and not the product name) isn't something that you add on to existing heating or generating solutions, but rather a complete system that replaces a conventional heating system with components that provide both heat and electrical generation. The generator is a Honda-made device that runs on natural gas or propane and produces 1.2 kW. The heat from the water-cooled engine is then captured with a heat exchanger and used to preheat or reduce the heating requirements of either the furnace or boiler which is providing warm air for the vents or hot water for the baseboards in the house. The furnace or boiler is of the 93-95% efficiency range like all of the high end systems of this type. The two units are installed in the basement of the house, vented to the outside as any heating equipment would be and are stuffed with all manner of monitoring and safety measures to prevent CO exposure in the living space.

It's really intended for use in areas where electricity is relatively expensive and gas is relatively cheap. The savings comes from better efficiency on the furnace/boiler (if you're replacing an old inefficient one) and then not paying for a good portion of your electricity. In warm climates or areas with cheap power and expensive fuel the payback will be less.

The system is appealing to people in places where wind and solar simply aren't practical. People in condos can't put up windmills in their backyards or panels on their roofs. Some people live in valleys where the wind just doesn't get to their house. Streets with historic houses may not permit any visible high-tech devices which would ruin the look of the area. Etc, etc. For these situations where the only option is replacing the equipment in the basement, the freewatt is the only shipping chp solution you can put in your house. Other benefits include internet support, monitoring and homeowner control.

Folks who have the option of, and desire to put in wind and solar installations capable of providing all of their heating and power needs aren't our primary customers. All systems that work - and there is a lot of hype and garbage available in all areas of energy conservation & management - have their place. I personally would love to have enough PV and wind at my house to go offgrid but that isn't going to happen. I'd be happy with a freewatt in my house but I don't have gas (either type) available. I'm a wood-burning guy. The debate over whether a fuel-burning device should be discussed in a forum of renewables or zero-footprint energy is something I'll leave to others.

I saw your question and thought I'd help straighten out the confusion. If you thought this was a device that you hook to the backup generator you keep at your off-grid solar house to capture the lost heat, you'd have to look elsewhere.

Howard Eglowstein
Principal Engineer
Climate Energy, LLC (designers of the freewatt)

BB. · December 2009

Re: Heat Harvester

Howard,

I read about the system a few years ago. At that time, they said the cogeneration system (basically a grid tied generator driven by a Honda motor and the "waste heat" used to warm the home--I gathered the motor cycled to provide heat for the home, and there was no "off grid"/emergency power function available) was being rolled out in just a few places in the Northwest US (IIRC).

Is it more widely deployed now?

Thank you for the background on the unit. I thought it was a very interesting solution at the time too.

-Bill

baldy672 · December 2009

Re: Heat Harvester

BB. wrote: »

Howard,

I read about the system a few years ago. ...

Is it more widely deployed now?

Your description is spot on for the standard warm air or hydronic installation. We've also added in domestic hot water using a passive tank on the hydronic system so those systems can get generator runtime (and savings) all year-round. Honda does have a version of the generator that with assistance can run when the grid is down. We've built a system around that which we're testing a limited number of until the new generator is shipping in quantity. In that version, when the grid goes down, we activate a custom (our design) controllable transfer switch to isolate the house, then restart the generator in a standalone mode. There's enough power to heat the house, keep your food cold and run a light bulb or two. When the power returns, our transfer switch detects that, tells the system to shut down and it restarts in grid interconnect state.

I don't know the number of installed systems. ECR has been recruiting and training new dealers every day, and these guys are getting product from ECR and installing it. We're a small group and the training and support of these new dealers (many of whom have never seen an internet connection before) is keeping us busy. We'd all like to sell more of what we make, but I'll bet the same is true of the wind turbine and solar guys. Many people who check us out end up buying one, but many people know at first glance that our system isn't for them. We're not likely to sell many in Florida, for example. Most of our systems are in our area south of Boston MA, but we have some in NY, RI, CT, MN, IL (I think), ME and NH.

I wasn't sure if I wanted to say anything in a solar/wind forum about a heating system that burns fossil fuel, but the word 'harvester' made me picture a little box that you attach to your Honda portable generator with nylon tie wraps. We're not that and I was hoping to clarify.
Howard

mike95490 · December 2009

Re: Heat Harvester

Thanks for the clarification of the co-gen unit. I did think it was some sort of shroud & zip-tie from the suspect handyman club page.

BB. · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

Howard,

Please feel free to continue the discussion here... We are a practical bunch and, even though the forum is funded/hosted by a solar RE retailer/wholesaler, the forum really takes a practical/conservation look at the whole energy usage around a home/business.

We encourage people to take the first three steps; 1. Conserve, 2. Conserve, 3. Conserve. (insulation, energy star appliances, sizing the use; such as using a laptop computer instead of a desktop, etc.).

Then look at reducing their electrical needs (cooking, heating, etc.) by transferring those loads to alternative sources of heat (natural gas, propane, solar thermal, etc.)... Then look at grid tied and off grid solutions to power the remaining, much smaller loads.

Personally, I think that your system falls very nicely into the forum discussions.

I believe that this is the home page for the Freewatt system and Howard's company if anyone needs more information:

www.freewatt.com

-Bill

baldy672 · December 2009

Re: Freewatt Cogeneration System

Thanks. I'm not going to pretend that I can convert any diehard solar fan and convince them to tear down their panels and buy a freewatt. I think the good solutions and products will continue to find market share and the snake oil will just (hopefully) go away. I'm happy to explain what we have if it's not clear. The actual numbers that go along with an installation (capacity, cost, payback, efficiency, etc) aren't something that I necessarily have to share, but I would prefer that people understand what it is we offer and then either explore or dismiss it based on real information. Like any complex installation, those details that everyone wants to know are highly dependent on the specific installation.

Yes, ECR's freewatt website is http://www.freewatt.com and it does try and explain the system in detail. How well it succeeds is sort of up to the viewer. This audience may find they want more information than the website presents - in that case, I'd suggest that interested parties can contact our or ECR's sales department and ask whatever they like.

I like your three first steps. One of the things our estimators would generally do when they went to a site for the first time is to talk with the homeowner about first fixing leaky windows, put some caulk around the seams, etc. If they're thinking about buying a freewatt to save money, why not start with something cheap that will have immediate payback? Now that the estimates and installations are handled by dealers, I would hope that they do the same. We certainly encourage them to do that when they're trained.

Howard

icarus · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

It certainly is an interesting concept, but I would be hard pressed to see the efficiency gains. I'm selling (net metering) 1.2 kws to the grid , yielding me ~$.1-.2 per hour. I'm putting ~12K BTUs into the house boiler. If those BTUs replaced propane (since propane BTUs and pricing are all I know,,,) it would be ~1/8 of a gallon of propane, worth ~ $.35, so I am getting ~$.37 worth of benefit from running this system? How many BTUs worth of natural gas am I burning to do this?

I am all for efficiency and co-gen is certainly one place to get some efficiency, but I have a hard time believing that a 1.2 kw Honda is more thermally efficient, even capturing it's waste heat than a commercial generating station, or more efficient that just burning Natural gas in the boiler directly.

Tony

BB. · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

I think the idea is that the "electricity" is near free (energy wise). So, you have a 95% efficient heater whose byproduct is (in more expensive regions) $0.20-$0.35 per kWhr electricity...

-Bill

icarus · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

But on a per BTU into the room basis, is it more efficient to burnt he fuel in the engine and capture the heat, or to just burn the fuel? I can't imagine a 1.2 kw honda running 24/7 to heat my house. 24/7, thirty days a month, 4 months a year=~3600 hours. What is the life expectancy of a little Honda,, even a Honda.

Wouldn't it be more efficient with a little diesel, since a diesel is way more thermally efficient?

I'll have to read a bit deeper into their web site.

T

baldy672 · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

These sorts of number are outside of my area of expertise. I don't buy gas for anything (I heat with wood & kerosene) and don't have a handle on what natural gas costs. And I'm a controls guy, not a thermal engineer.

A couple of numbers I've got that came from the web and the Honda manual might help.

The Honda requires 5.2kw of gas (that's how it's listed on the technical sheets) to generate the 1.2kw of power and 11K BTU of heat. A Google search turned up the figure of about 10 kwH per cubic meter, so unless I got my math wrong, making 1.2kwH of power should take 5.2/10 or about 0.52 cubic meters of gas. A national survey of gas prices a few months ago showed a *high* price of $12 per thousand cubic meters, or $0.12 per cubic meter. This is a high California price and people in Mass apparently pay a lot less than that. Even in this worst case scenario, the 1.2kwH ought to cost 0.52 * 0.12 / 1.2 or about 5 to 6 cents per kwH. Again, if your gas prices are less than that, the cost is less than 5 cents. Plus you're also getting 11K BTU/hr of usable heat. In our area of MA, 1 kwH of electricity goes for about 20 cents, so only counting the gas you buy and the electricity you don't, you could be saving 15 cents or more for every kwH you generate. If it's power you didn't need, the utility would be paying you 20 cents for it.

Depending on the size of your house and how tight it is, you'll get more or less generator run time. Figure in some number (perhaps as high as 4000 hours for a winter). Add in some savings for the saved heat. Subtract something for the additional cost of the hardware over a non-cogen system and the scheduled maintenance. Some of our customers live in areas where they get rebates from either their utility or the gas supplier on the cost of fuel, so that helps too. Like (I'm assuming) solar, wind, or geothermal, it's a complicated formula that has to take quite a few things into account.

It's not the silver bullet of energy and money savings. I think we all agree that a tube of caulk, a CFL, or learning to turn off unused lights will pay for itself far faster than any tech contraption we can think of to save energy. Like anything else, you need to ask yourself what your goals are - why are you looking at alternative heating/energy? To save money? To lessen your dependence on the grid? To consume fewer resource and save the planet?

I've seen numbers that take the amount of emissions made by the power plants to make the amount of electricity they have to produce to get the 1.2kwH into your house after distribution loss and compare it to what comes out of our equipment. We do better, so that makes some people happy. Saving $600 a year on your electric bill makes some people happy.

Please feel free to correct my numbers if I did my math wrong above. Honda claims an 85% efficiency extracting energy from the gas. That's clearly less than the 95% you can get by burning the same gas in the boiler directly. You win because electricity is far more expensive than gas. If the situation were reversed - you live in a cheap power area and have to fly in your propane by air - then this system wouldn't work at all. And as you said, propane is different than natural gas. I don't know the consumption rate of the propane-powered generators.

I don't mean to handwave or bail on your question, but we've got people who are far more qualified to work out numbers for a particular situation. You do have to know the prices of power and gas in your area, etc. Without that information it's hard to estimate costs or savings effectively.

Howard

baldy672 · December 2009

Re: Heat Harvester (Freewatt Cogeneration System)

icarus wrote: »

24/7, thirty days a month, 4 months a year=~3600 hours. What is the life expectancy of a little Honda,, even a Honda.

Wouldn't it be more efficient with a little diesel, since a diesel is way more thermally efficient?

The scheduled service is an oil change, spark plug change/check and valve adjustment check at 6000 hours. When I joined Climate Energy three years ago, there was a room full of generators running 24/7 for over 2 years. They were all approaching their third oil change. Honda tore down a few of them and declared them to be mostly wear-free and in good shape to go for the next 6000 hours. We needed the space so we emptied out that lab and stopped the test.

I wouldn't hold my breath waiting for the generator to run the same (almost) 50 years the gas boiler has run in my parents' house, but we've seen samples running for 5 years using your numbers and showing no signs of stopping. And consider that you weren't allowing for the generator to stop. In reality, we're also talking about houses where someone bothered to buy that tube of caulk, fix that broken window and blew in some extra insulation. The generator wouldn't have been running 24/7.

Honda isn't putting a number on the estimated life of these things because I think they simply don't know. The design has been around since 2003 (first installations in Japan) and I think some of the early systems are still running just fine. Mechanical things do wear out and the same questions would be fair for wind turbines.

I don't know about diesel efficiency, but I'd imagine all sorts of issues with fuel quality (not an issue with natural gas), exhaust and the comparative dirtiness of the diesel compared to a natural gas engine. Who would want a diesel engine in their basement?

Howard

Heat Harvester (Freewatt Cogeneration System)

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