steam recovery to heat greenhouse

Ben Wiles

How would one go about recovering steam produced by a boiler to heat parts of the building which are not heated. I am thinking about steam normally emitted by commercial builings or municipalities. Also, are boilers on continuously during the winter? I ask because I need to have a constant heat source. I am a student studying sustainable development. If you have any ideas please feel free to pass them along.

Thanks,
Ben Wiles

Tom Anderson

Thermal Greenhouse Recovery

Using waste heat from a power plant for utilization in a greenhouse is a viable concept..... if I understand you inquiry correctly.

In fact, such a design concept won the ASHRAE innovative design/efficiency award one year in the early 90's.

After all, the heat would otherwise be dumped directkly into the atmosphere via cooling towers. Of course, one must consider heating neds of a greenhouse when the power plant is down for service/maintenance.

Hope this helps........

Art Pittaway_2

Recycled steam

Good question, if you want to see a greenhouse that will lock your calculator, visit the Archer,Daniels,Midland Company (A.D.M.) in Decatur, Illinois. Or contact them and see if they have info they can send. They process grain and make food products of all kinds. The company has several acres under glass and all winter it produces cucumbers, lettuce, etc. from "waste" steam.
Now to correct part your question...when part of a steam system is shut down the boiler runs less and doesn't produce excess steam. If your referring to the trail of "smoke" from the boiler plant, that's exhaust from combustion, like when you see a car exhaust in winter it's smoking but it's not steam. In fact, some commercial and muni. buildings use cooling towers to cool the building in winter and the vapor off the building is in fact cooling not heating. Many buildings have internal heat created by lighting and computers, etc. that exceeds the heat loss of the building.
Now, steam is a wonderful form of energy and in high pressure applications (100+psi) the steam can be used at lower and lower pressures until almost all the energy is gone. This requires controls, valves and piping and a place to use the energy.
I'm not sure what sustainable development means in your case, and constant heat source. Your question is huge and the data goes back 100 years. You are going to have to narrow down and define your goal. Then try to understand a subject that many of us have spent 20+ years trying to figure out.
Some companies you might try for info are: I.T.T. Industries (Hoffman Specialties); Spirax/Sarco,Co.; Burnham Boilers; Cleaver Brooks Boilers; Yarway Corp.;
Good luck with your project.

David Efflandt

Electric utilities may have surplus steam.

Milwaukee has steam from the electric power utility piped out Wisconsin Ave. to heat downtown buildings (they don't want steam condensing in the turbines). Of course if the steam is still high pressure you need regulators and relief valves. Delivery (steam piping, etc.) would be the expensive part if it is any distance away.

I also saw one of the boilers that was shutdown. I forget how many stories tall it was, but looking up inside was copper tubing as far as you could see. They pulverize coal into a dust fed in from the top. Took a couple of days to fire them up or bring them down.

David Efflandt

Electric utilities may have surplus steam.

Milwaukee has steam from the electric power utility piped out Wisconsin Ave. to heat downtown buildings (they don't want steam condensing in the turbines). Of course if the steam is still high pressure you need regulators and relief valves. Delivery (steam piping, etc.) would be the expensive part if it is any distance away.

I also saw one of the boilers that was shutdown. I forget how many stories tall it was, but looking up inside was copper tubing as far as you could see. They pulverize coal into a dust fed in from the top. Took a couple of days to fire them up or bring them down.

I also see manhole covers mark steam in Chicago.

David Efflandt

Electric utilities may have surplus steam.

Milwaukee has steam from the electric power utility piped out Wisconsin Ave. to heat downtown buildings (they don't want steam condensing in the turbines). Of course if the steam is still high pressure you need regulators and relief valves. Delivery (steam piping, etc.) would be the expensive part if it is any distance away.

I also saw one of the boilers that was shutdown. I forget how many stories tall it was, but looking up inside was copper tubing as far as you could see. They pulverize coal into a dust fed in from the top. They preferred not to downfire them, which required supplementing more expensive fuel oil to keep the fire burning. Took a couple of days to fire them up or bring them down.

I also see manhole covers mark steam in Chicago.

David Efflandt

Electric utilities may have surplus steam.

Milwaukee has steam from the electric power utility piped out Wisconsin Ave. to heat downtown buildings (they don't want steam condensing in the turbines). Of course if the steam is still high pressure you need regulators and relief valves. Delivery (steam piping, etc.) would be the expensive part if it is any distance away.

I also saw one of the boilers that was shutdown. I forget how many stories tall it was, but looking up inside was copper tubing as far as you could see. They pulverize coal into a dust fed in from the top. They preferred not to downfire them, which required supplementing more expensive fuel oil to keep the fire burning. Took a few days to fire them up or bring them down.

I also see manhole covers mark steam in Chicago.

Tony Conner

It's Not Really...

..."surplus" steam. There can be extraction points on turbines where steam is pulled out for other uses after it has partially expanded on it's run through the turbine. Where & when this happens is an economic calculation. Does it make more financial sense to let that steam keep driving the turbine until it hits the condenser, or pull it out of there, and heat something...like a greenhouse?

The boiler tubes will be some kind of alloy that will take the pressure & temperature within (those boilers likely operate at 2 or 3 thousand PSIG) and the heat of the furnace, as opposed to copper.

There are always a lot of factors to consider. What is the most mechanically efficient, may not make the most economic sense. A BTU is a BTU, except when you start to put a $ value on them. Electrical BTUs are typically the most expensive. Cooling BTUs are next, then heating BTUs are the cheapest. Greenhouses are huge energy eaters both electrially and thermally. If it's a new greenhouse designed for hot water heating, steam very near the end of the run through the turbine can be used to make hot water (maybe 180-200*F) through heat exchangers, and pumped through them. There's also usually something that can be considered for an on-site cogen plant. Often, it's a diesel engine converted to natural gas, driving a generator. Heat from the jacket and lube oil coolers is recovered, but far and away, the biggie is the engine exhaust.