Waste Energy Utilization

So far there have been very few systems that have been economical to build and operate over the long haul. Exhaust gases tend to be corrosive and when cooled too much will combine with water and rust the exhaust system. Radiator heat is usually under 220 d F, and at that temperature has limited applications for heat recovery.

As the price of oil increases, there may be a point where the economics may justify the cost of energy recovery.

i am sharing my reallife experience in waste heat recovery it may sound funny.I was Cheef engineer in one of shearton hotel in the year 1984 our Hotwater generators brokedown requiring long replacement period,immidite restoration of central hot water system was a challange. we connected heat exchanger of our 500Kva Cummins Diesel generator to hot water storage tank by passing cooling towers with a changer over valve and restored hot water supply it took three months to replace hot water generator coils and re commission the same.Till then i was using engine heat exchanger as source of hot water.we continued using the same system and saved couple of 100000 Indian Rs in terms of Fuel burnt in the hot water generator. The idea of using engine heat exchanger was born to save my skin.

crm

If you have a coolant which actually cools the engine and that coolant is greater than 80degrees Centigrade, you can power an ABSORPTION chiller for airconditioning and minor high temp refrigeration purposes. Such chillers are available from most US manufacturers

There is a 6-stroke cycle that may be of interest. Remember suck, squeeze, bang, blow? Add on 'squirt, chuff' for the fifth and sixth strokes, as water is injected into the cylinder, utilising its tendency to become steam as a second power stroke and using up the heat that would otherwise be rejected before doing something useful with it.

The technique has been listed ad nauseam in these columns before, and there is an entry giving more information in Wikipedia for the interested reader.

We do a lot of these stuff here. This is known as WHRB (Waste Heat Recovery Boilers) from Turbine/Gas Engine Exhausts. On a 1 MW Gas Generator you can get 1000 to 1200 kg/hr at 12 Bar. On most Engines (Caterpillar etc) except Janbacher (800 kg/hr) Govaskar ( maybe 500 kg/hr). On Gas Turbines you can get upto 3500 kg/hr. All yet again, depends on the exhaust gas temperature and volume of waste heat as dictated by the Manufacturer plus the hours of operation.

We then inject this steam into our steam distribution system.

Should you require more steam you can add auxihillary burners on the WHRB.

You can also opt of WHR Boilers for Hot Water. This we then utilize on Hot water chillers to get free air conditioning.

Maximum saving in my country on a 1 MW Gas Generator is USD $ 12000/month average 720 hrs/month operation. The payback on the WHRB is within 10 months.

Just this year I sold 18 WHR Boilers (Simplex & Duplex) of make Garioni Naval,Italy

You can check their site for details on these type of Boilers: www.garioninaval.com.

Am a consultant too to a big Textile Mill where we have 4 Caterpillar Gas Generators

1 MW x 4 = 4 MW all with WHRBs and we are getting steam veraging .8 T/Hr or 3200 kg/hr max and minimum 2200 Kg/hr (depending on operation of the Generators, less machines in operation or some Generator on maintenance). This has now been in operation over 5-6 years. Next we utilize the Jacket Cooling water 23-24 M3/hr (68-70C) for our Process Hot water requirement to save steam at all washing tanks of machines: Bleaching/Mercerizing/Pad Steam dyeing etc.,

(We also utilize the waste drain of all washers at 90C to pass via a heat exchangers to drain and fresh water is then heated via the heat exchangers to the washers further saving steam - this then is not a part of your question)

I have installed number of these waste heat recovery boilers (HRSG)along with Gas turbines where the quality of exhaust is clean the same apply to gas engines when it comes to Diesel fueled power plants the exhust is not clean and will mess up the HRSG functioning this is my experience

crm

Here is an idea to use a car engine's "Waste Heat" to heat a home while generating electricity

I sent a letter on this to Honda Power Equipment Co. on March 22, 2001. but got no response (I still don't see one on the market):

A great product to make would be a Home Furnace that is actually a Natural Gas Engine driving an Electric Generator. The heat from the engine would be used to heat the home by circulating hot water, or by using a heat exchanger for circulating hot air.

The electricity generated would be pushed onto the power grid and sold to the electric companies. Recent developments in electronics allow the generator to be smart enough to disconnect from the grid in case of an electric power failure. A secondary advantage would be to use the generated electricity to support the home during a power failure.

The Honda Hybrid (car engine) is in a position to jump into this market with only minor modifications. Some of its most relevant features are:

- Ability to start up & shut off on demand.
- The engine is already coupled to a generator. (But will need the windings changed for home voltage.)
- High efficiency engine.
- High Honda quality/reliability

With the rising shortages of both electricity and fuels, both highly efficient furnaces and spot sources of electricity will be in increasing demand.

By redefining what the "useful energy" output from a machine is, we can hedge on the laws of thermodynamics to allow efficiencies nearing 100%. In this case, the heat output is not "waste" it is one of the "useful energy outputs", along with the generated electricity. Why wait for fuel cells when we have the technology to build these engines NOW.

I think Honda is almost there, based on a post I saw a couple of months ago.

thank you , can i operate sterling engine , if yes where do i find such engine manufacturers , how do i calculate energy recovered (submited to sterling cucle) ,i suppose that if such engine can generate enough power to ac , electricals ,power operated accessories what units do we put with the actual amount of fuel utilised for whole .

Yes, the waste heat output of an IC engine is ample to run a small Stirling engine. There are various people and groups working on units, including some commercial units and kits. You could Google Shop for books, plans, kits, etc.

Have fun.

I actually am working on this as we speak. By working on it I mean I have design/prelim drawings and am in need of some solid math.

It is exactly why I came to CR4 to begin with.

I have a philosophy re: these types of problems. The lever, the screw, block and tackle; these are fundamentally sound machines. In keeping with simplicity, lets re-evaluate the machines as we employ new materials and applications. Further this with the idea of a symbiotic relationship between fuel and waste and let's see what we can manage.

I feel that your problem is worthy of time and energy (no pun). I am anxious to present mine as well. Alas, proprietary. :( For now :)

Am willing to talk and or meet with any who want to discuss in more intimate detail give understanding/acceptance of proprietary issues.

Just for kicks. What does anyone have to say about a device (gear) that is moved by a very heavy and very light gases in opposition?

cr3