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By Russ Finley on Apr 9, 2012 with 9 responses

Solar’s New Competitor

Last week, Kate Galbraith wrote an article in the New York Times with the headline A Competitor Emerges for Solar Panels, which is  somewhat nonsensical.

It’s about the small co-heat and power (C.H.P) electric generator and hot water systems available for residential homes. This technology is not just emerging. I wrote an article about these five or six years ago when they were first marketed in Japan.

The article suggests that you can sell your excess power back to the grid (which I could not confirm), like is done with solar panels, and I suspect that is why she thinks they compete with solar, but solar panels “generate” zero emission renewable energy. These C.H.P units “consume” a non-renewable GHG emitting fossil fuel. Cogeneration competes with other energy consuming devices like 95% efficient condensing forced air gas furnaces and heat pumps. It’s an apples to orange comparison when it comes to solar.

 … it would often take homeowners 10 years to make back the cost [for a C.H.P. unit], in the form of lower utility bills … People are willing to pay a lot more money for solar panels than what a C.H.P. system would cost.

Fossil fuels are hard to beat when it comes to cost. Depending on where you live, the payback for solar hot water can be as short as four years or as long as eighteen. Solar photovoltaic has a much longer pay back period than solar hot water, but then again, it’s like paying extra for a hybrid car, in that some consumers want to use less fossil fuel, and are willing to pay extra to accomplish that. Think of solar as the ultimate high end appliance, like a fancy stove or refrigerator. If payback is all that matters, explain to me why people drive Cadillacs.

Let me explain what these systems are and how they work (anyone familiar with the concept can skip this paragraph). I’m doing this should Galbrith ever read this article because, as her headline suggests, she doesn’t seem to have a very good grasp of the concept.

You connect a gas motor, similar to the one on your lawnmower, to an alternator, similar to the one under your car’s hood. This combination is typically called a generator set similar to the ones you can buy at hour local Home Depot. Next, you wrap copper tubing, like the plumbing in your house, around the alternator and motor exhaust pipe and pump cold water through it. The waste heat from the motor and exhaust will heat the water which will be sent to a hot water tank. Instead of using gasoline to run the engine, you use natural gas or propane.

There are hot tub designs out there that are heated purely by the waste heat captured from the pump motor that has stainless steel tubing wrapped around it. There are no heating elements.

 Small systems are gaining traction in Japan after the nuclear disaster last year, which led officials to order that nearly all of the country’s reactors be [temporarily] taken offline. Orders have “increased dramatically” since that event and are likely to rise even more sharply in the future, …The home systems in Japan tend to be much smaller than those in Germany or the United States …

High-end motor homes (the kind that rock and country music stars tend to travel in) have been using quiet built-in propane powered generators for decades, although nobody I know of bothered with capturing the waste heat. The Japanese apparently are turning to them because their government is failing to provide its citizens with adequate electrical power at affordable rates.

Several homes in my neighborhood have natural gas powered generators sitting in their backyards tied into their breaker panel in case of power outages. The systems being sold in Japan typically produce enough to power something like a toaster oven, or instead, some lights, laptop, router, and television, and enough waste heat for much of their hot water needs, but not for all home heating needs. And that is why you still need grid power and an additional heating system in addition to the C.H.P. unit.

You have to remain connected to the grid because these units can’t handle big loads like a clothes dryer, or stove, or fridge, or hair dryer and latte machine at the same time. And when your load is low, it sends power to the grid, spinning your meter backwards, assuming you need its waste heat. But if you are full up with hot water, it never comes on. You draw electricity from the grid.

There is no free lunch. These systems lower your electric bill but increase your natural gas bill. Ignoring the costs of the system, you should save money if your electric rates are high enough and your natural gas rates are low enough.

These systems are not typically designed for emergency power. They won’t work in a power outage (they have no battery to start the engine). You pay extra for that feature. And if you are concerned about GHG emissions, keep in mind that these systems burn a non-renewable fossil fuel, just like my 95% efficient gas furnace does.

As a consumer, you have to be careful. I have a neighbor who spent a lot of money to buy a hot water heater that has a heat pump on top of it. A heat pump grabs energy out of the surrounding air and sends it someplace, in this case, into a hot water heater. He didn’t realize that this acts like an air conditioner in the middle of winter, causing his furnace to run longer. There will be no net energy gain, no money saved.

In conclusion you will gamble $10,000 in hopes of saving $10,000 over a decade while burning a fossil fuel the whole time. If I’m going to gamble I’d rather do it with a solar hot water system, possibly combined with a heat pump like my neighbor, but located outside my home’s insulation envelope.

Photo courtesy of Marion Doss via Flickr.

  1. By Peter Leppik on April 9, 2012 at 1:11 pm

    CHP is essentially a form of energy arbitrage: taking advantage of the gap between the relatively low cost of natural gas and the relatively high cost of electricity. You’re going to burn the gas for heat anyway, so why not skim some of that energy off the top and turn it into electricity at a profit?

    CHP may not be as green as solar, but it does have some significant environmental benefits:

    1. Most power plants do not currently capture waste heat, and so discard most of the energy in the fuel. CHP uses nearly 100% of the energy in the fuel, and reduces the amount of fuel burned in non-CHP plants. This reduces the total amount of fuel burned system-wide.
    2. If you line in an area where most electricity comes from coal, home CHP replaces some coal-based electricity with natural gas. This leads to a substantial reduction in the amount of GHG required to generate that electricity.
    3. Generating electricity close to the point of use reduces transmission losses, again reducing the amount of fuel needed system-wide.

    Here in Minnesota, for example, CHP could offset a substantial amount of a home’s winter heating bill while reducing the amount of fossil fuels burned in our state’s power plants. I don’t see how that’s anything but a win.

    • By Russ Finley on April 9, 2012 at 3:31 pm

      I like the concept as well but pay back times claimed by manufactures are guaranteed to be exaggerated.

      If all you use it for is hot water, it would not save energy once you have enough.

      If you have to install a boiler heater system to utilize all of its waste heat, the cost would be much higher than advertised.

      Like solar, payback times would be highly dependent on location, cost of heating system etc.

      Would your system pay for itself about the time it needs to be replaced? I’m also skeptical that a small internal combustion engine would reliably run nearly continuously in a cold winter and  maintenance free for a decade.

      But my larger point is that these should not be viewed as a replacement for solar.

      I’m sure it would save people money over the long haul in the right circumstances.

      Your point about the system using less fossil fuels is a good one, assuming you don’t live where most of your electrical power comes from nuclear or hydro.


  2. By notKit P on April 9, 2012 at 6:13 pm

    “I don’t see how that’s anything but a win. ”


    I always find it amusing when people think they can do a better job of producing power than the experts that do it everyday.


    For example a large city has a coal plant 20 miles from the city that is carefully regulated to minimize emissions so that air quality is not affected. Adding a million CHP units in the city will have a significant effect.


    For CHP to be cost effective you need a large demand for how heat/water all year.


    “run nearly continuously in a cold winter and  maintenance free for a decade. ”


    Energy is a cheap commodity. Making your own as a hobby is boring and expensive. Systems fall into disrepair after the cost a few services calls. That is assuming the coroner does not visit first.


    • By Russ Finley on April 9, 2012 at 8:01 pm

      You make some good points. Getting your electricity from two wires that come to your house is pretty nice. I’m also glad I don’t have to maintain my own sewage system or water supply. Now to find a way to get rid of my furnace, air conditioner, and hot water heater.

      I have a friend who used to do most heating with a wood stove. He finally gave it up because it was a lot of effort for little return.

      For example a large city has a coal plant 20 miles from the city that is carefully regulated to minimize emissions so that air quality is not affected. Adding a million CHP units in the city will have a significant effect.

      Hadn’t thought of that, analogous to having too many wood stoves in a city. RR mentions the effectiveness of controlling pollutants from a single source in his book.


  3. By Herm on April 9, 2012 at 9:25 pm

    No idea why these are $10k systems.. its a single cylinder Honda engine running on NG,  plus a generator.   If you dont need hot water the engine stops… at 30% engine efficiency the system produced 1500W of electricity and 5000W of heat.

    Better to use the 1500W of electricity to run your fridge, or speed up heating hot water than making the meter run backwards.. the power company wont pay you much for that electricity.


  4. By Captain Obvious on April 10, 2012 at 8:34 am

    If you can use the generator as a backup, that would greatly increase its usefulness. You need to run it off NG or propane, not gasoline; I’d prefer a fuel cell (Bloom Box type) if the costs can come down. This avoids the high transmission inefficiency of the grid (plus taxes and profit); many rural houses can run off-grid. Solar for DHW and space heating is a no-brainer because it’s low temperature, low tech; but the sun doesn’t always shine.

  5. By Tom G. on April 10, 2012 at 1:49 pm

    Russ gave me a real chuckle with the title of this posting.   It’s not that I think generators don’t have their place in life since I do have one for emergency standby power.  BUT, having said that, let’s do a little simple math to see how efficient or inefficient standby generators can be.

    I went to the Buffalo website and found a similar sized generator [couldn't find the exact model shown].  According to the specifications an 1850 watt generator will use about .21 gallons of fuel per hour [11 hours run time @ 50% power on 2.3 gallons @ about 900 watts].

    Let’s see; that is about 5 gallons of fuel for each 24 hour period or about $20/day [$4.00/gallon] at current gasoline prices.  Put another way, about $602/month for fuel.  I didn’t take the time to calculate the current price of natural gas, figure in the depreciated cost over time of the generator, wear and maintenance, value of electricity over a years use or any other factors.  Just the bare cost of operation.  By the way, most well engineer generators have a life expectancy of about 2000 hours or 83 days in continuous operation.   Here is a fun calculation; multiple 3600 rpm X 60 minutes X 24 hours X 83 days.  How many times has the piston went up and down in the cylinder?        

    So $602/month for fuel sounds high but we then need to figure in the value of the waste heat or hot water created.  On my electric water heater there is a decal which states that based on the utility rates in my area it will cost me $544/year or about $45/month for hot water.  So I need to deduct that $45 from the $602 which leaves an expense of $577.00/month.  I also need to deduct the value of the electricity produced by the unit [1 kW/hr @50% power level X 24/hrs @.12/kW = $2.88/day X 30 days = $86/mo.] .  So now we are down to just $493/mo.  

    This $493/month happens to be about 3 times more than my current electric bill for my all electric 3 bedroom, 2 bath house.  And we are not talking about a huge amount of power are we.  One [1] kW per hour is about enough electricity to run a small window unit AC unit or a washer and gas dryer or a couple of small electric motors.  Don’t even think about trying to run a typical electric stove or electric dryer. 

    Now there are lots of different ways to shot holes in my little story because I didn’t take a whole bunch of stuff into consideration.  Things like the installation of a service disconnect switch to feed your excess power back to the utility which can be expensive.   Of course I forgot to mention that your utility will most likely want to inspect your installation to ensure it will not harm any of their equipment.   I also didn’t figure in the capital cost to build, run and maintain your own co-generation system.  Did I mention your neighbors might not enjoy the noisy generator, LOL.  

    That doesn’t mean they don’t have a purpose in life – it only means they are best suited for emergency use or in something like an RV which is frequently not connected to a power grid.   But for everyday use – I will stick with solar hot water and solar PV.  Both can be installed on my roof and for the most part [if it rains every once in a while]  I can forget about them for the next 20 years or so.  BUT I will be the first to admit they will cost more than the generator – or is that really true? 


    • By Robert Rapier on April 10, 2012 at 2:47 pm

      Now there are lots of different ways to shot holes in my little story because I didn’t take a whole bunch of stuff into consideration.

      The biggest thing is that you aren’t taking into consideration the hot water for heating the home. Your hot water is for showers, dishes, and laundry, but many homes (such as my house in Germany) are heated by hot water pipes underneath the floor. If a house has a near year-round demand for hot water for heating the home, the efficiency of a CHP system is very high and the savings can be substantial. If the hot water produced is far too high for the home (or any user in the vicinity) then the utility of the CHP system declines.


      • By Tom G. on April 10, 2012 at 2:56 pm

        In a condition where year around heating [100% duty cycle] is required, how does a CHP unit compare with the cost and efficiency of a ground source heat pump @ a COP of 3.0? 

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