Cost to generate steam?

hot_rod

Ray, some excellent info here to help prove your point.

http://www.spiraxsarco.com/Resources/Pages/Steam-Engineering-Tutorials/introduction/steam-the-energy-fluid.aspx

RayWohlfarth

@ChrisJ That is so true. So why are heat pumps and AC systems are often considered "green" and Steam is an energy hog?
@hot rod Thank you so much I will use that in my seminars. You are a plethura of information. You are like the wise man on top of the mountain we visit for your sage wisdom LOL

ChrisJ

RayWohlfarth said:

@ChrisJ That is so true. So why are heat pumps and AC systems are often considered "green" and Steam is an energy hog?
@hot rod Thank you so much I will use that in my seminars. You are a plethura of information. You are like the wise man on top of the mountain we visit for your sage wisdom LOL

Because all of the steam systems people associate the term with were broken.

That, and new produce is always pushed as better, no matter what the real case is.

I don't blame anyone for that, companies survive by pushing produce and people in general always want new.

The Steam Whisperer

HR, you bring up several good points about convective currents of hot steam rads and the radiant losses to walls etc. Gerry Gill's website has a study from the 1920's completed at University of Illinois about radiator covers that touches these subjects. The type of radiator cover in use effected the distribution of the convection air off the steam radiators. The optimum designs increased the air temps in the lower 6 foot of the room and decreased steam consumption by 5% or more (IIRC). Losses behind high temp radiation to exterior walls are high, I bet. The city of New York's recent energy saving guide recommends insulation be added behind the radiators as one of the primary recommendations.

For an apples to apples comparison, air temp is a very bad standard, IMO, as it does not accurately relate to comfort levels. A wet bulb, black body type temperature reading device has proven to be much more accurate. This device is effected by air temp, radiant temp and humidity. This follows some of the design parameters of the psychrometry charts that much more accurately predict human comfort levels than just straight air temp. I. E. a room at 72F and 80% humidity ( typical oversized cooling equipment) is much less comfortable than one at 78F and 50% humidity ( slightly undersized cooling equipment).



A real test is going to have to be completed over a complete heating season. This takes into account the variables on how the system interacts with the building while maintaining human comfort. A hot air system will probably perform better in warmer weather due to quick response time needed to" take off the chill" in spring and falls' cool, damp weather by warming air temps and somewhat drying out the air. In mid winter, however, something with increased radiant capacity that does not dryout the air will probably be far superior.

RayWohlfarth

thanks @ChrisJ People always like the shiny new toy
@The Steam Whisperer (Formerly Boilerpro) You are correct. A forced air furnace can be measured by calculating the temperature rise over the volume of air while radiation cannot as it does not heat the air and only the objects. Hence my quandry. LOL

The Steam Whisperer

Ray,
Even the temperature rise number is incorrect, unless you remove the heat energy the fan has put into the air stream. This is where the efficiency numbers of furnaces appear to be inflated... they don't take out the heat from the fan motor. This has some impact on hot water boilers too ( heat from pumps), but not nearly as much. Some calcs that I have done to remove this motor heat from the efficiency numbers for furnaces shows about a 2 to 3 % inflation of the efficiency. It has an especially big impact since the overall grid efficiency of electricity is about 30%, whereas the delivery of natural gas grid is about 90% or higher.

RayWohlfarth

@The Steam Whisperer (Formerly Boilerpro) didnt think of that. They may contend the heat is not wasted as it used for heating the space. In the summer, it will cost them more.

The Steam Whisperer

However, they appear to assume that the extra heat is created by the gas combustion process, so it inflates the gas efficiency numbers. Its usable heat, but its also essentially electric heat and very costly. In the summer its a real double wammy, you pay for the power to run the motor and then pay for the power to provide additional cooling to compensate for the motor heat. If you figure that's a 3/4 horse blower, that motor is probably about 850 watts, which is about equal to 3000 btu/hr or an extra quarter ton of cooling in whats probably a 2 1/2 ton system. That's 10% of the system capacity just to cool the motor or about a 12% drop in efficiency. I've contended for a long time that window units can be more efficient than central air, and this is part of the reason why... window units put that motor heat in the outdoor airstream not the indoor. It also a contributer to better efficiency of ductless systems... much less power used in the space for distribution.

hot_rod

The Steam Whisperer said:

HR, you bring up several good points about convective currents of hot steam rads and the radiant losses to walls etc. Gerry Gill's website has a study from the 1920's completed at University of Illinois about radiator covers that touches these subjects. The type of radiator cover in use effected the distribution of the convection air off the steam radiators. The optimum designs increased the air temps in the lower 6 foot of the room and decreased steam consumption by 5% or more (IIRC). Losses behind high temp radiation to exterior walls are high, I bet. The city of New York's recent energy saving guide recommends insulation be added behind the radiators as one of the primary recommendations.

For an apples to apples comparison, air temp is a very bad standard, IMO, as it does not accurately relate to comfort levels. A wet bulb, black body type temperature reading device has proven to be much more accurate. This device is effected by air temp, radiant temp and humidity. This follows some of the design parameters of the psychrometry charts that much more accurately predict human comfort levels than just straight air temp. I. E. a room at 72F and 80% humidity ( typical oversized cooling equipment) is much less comfortable than one at 78F and 50% humidity ( slightly undersized cooling equipment).



A real test is going to have to be completed over a complete heating season. This takes into account the variables on how the system interacts with the building while maintaining human comfort. A hot air system will probably perform better in warmer weather due to quick response time needed to" take off the chill" in spring and falls' cool, damp weather by warming air temps and somewhat drying out the air. In mid winter, however, something with increased radiant capacity that does not dryout the air will probably be far superior.

But our customers want to see that dial on the wall. We tried promoting thermostats without any temperature numbers and the general public couldn't handle them I've found regardless of the radiant and comfort spiel I still see stats at 70- 72F.

The point you brought up about the type of building the system in matters. A time was they didn't insulate attics, or very little. Now R30- 50 is common, so that is the highest R in most homes. That stratified 85F against the ceiling is not as much as a concern if you trust hot goes to cold and the wider the ∆ the faster the transfer.

The biggest load is doors and windows, don't see that ever being much more that R-3- 7. So a 180F radiator under an R-1 window presents that huge ∆ transfer potential, acknowledging the energy transfer is both radiant to the objects as well as convection currents from radiators. Heat load programs are good for showing the % of where the lose is in the structure.

I'd still say it takes X amount of energy to keep the inside warmer than the outside of the box, regardless of where the hottest surfaces and losses are.


I think what Ray will find is the "fuel to heat the energy" is the tripping point. I don't think 180F rads compared to steam rads for example will show much if any operating cost difference, assuming both are 83% boilers? Unless they use condensing steam boiler technology:)

Applying the comfort factor into the operating cost comparison is a different question. I can keep my living room at 60 and sit in front of the wood stove and be comfortable.

If the question is mainly cost to maintain temperature I think the more efficient boiler wins.

Solid_Fuel_Man

Ok, some real electrical numbers from my own system.

Standby boiler 0.04A
Standby ZVC 0.20A

Total standby power consumption 0.24A

Boiler running at 60%, CH circ on speed 3, radiant pump on speed 2, ZVC on, several 120Volt ice cube relays for logic, etc. 1.74A.

1.74amps x 120volts = 208.8 watts total system power consumption.

Local electric rate including all taxes, delivery charges = $0.157/kWh

.157 /1000 = .000157

.000157 x 208.8 = $0.0327816 for an hour

Electrical Cost to run entire system with boiler running at 60% modulation rate for a week.

$0.0327816 x 24 x 30 = $23.60 a month.

The boiler never runs at 60% and never for 24 hours for 30 days. I'd estimate a realistic electric cost of $15 a month on a worst case scenario.

The Steam Whisperer

Sounds like you have a mod con. If the heating curve is set tight to the actual heat loss needs, I would think the pumps would be on nearly continuously most of the winter and the boiler output would just modulate up and down. Sounds like your curve setting is high.... running a lot hotter water than necessary to maintain steady temp.

leonz

Hello and good morning Mr. Walforth,

I hope you will forgive this oversight on my part but I neglected to add this earlier.

A hot water boiler used for a gravity hot water system using radiators should also be added to your spread sheet as a possible option as the service life of the system will be more than a century
and added to that there are no moving parts except in the case of a feed water pump to fill the open to air expansion tank if that method is used for a back up boiler.

The larger 4 inch stand pipe coming from the 260S boilers steam chest for a gravity system has been in use since 1947 if I remember the date year correctly. The 260S has two 2 inch return tappings in the boiler sump.

Adding gravity fed a hot water back up boiler should be added to the spread sheet as you could employ a water receiving
tank in the basement for the gravity hot water system using a common return header to the back up boiler sump as a consideration.

You would have even more thermal mass to use for the back up boiler as the coal stoker will not require a storage tank to hold thermal mass as it would barely run to heat the water if the storage tank was used to feed the boilers pair of 2 inch sump lines as the boiler would be at or near steam temperature to create the flow of hot water needed to fill the open to air expansion tank and the hot water radiators below the attic.

Just as an example the Axeman Anderson 260M traveling grate
coal stoker will provide 260,000 BTU for steam with 240 BTU per foot for 1080 square feet of radiation.
This boiler used with hot water heating will provide 1730 square feet of radiation.
I do not know how old the performance figures are or whether they were calculated using gravity hot water heat or a hot water baseboard and I am not sure if this testing method used the "all windows open method to heat a home in winter at or below the freezing temperature"

jumper

I presume that folks attending a steam seminar are industrial or commercial users. Steam goes into unit heaters and maybe some jacket heaters. If they switch to hot water the circulator will run continuously. The few hundred dollars electric is insignificant for such users. The questions are:
• is a hot water heater or a steamer easier to live with?
• what is more useful,steam or hot water?
The answer to the second question in my opinion is steam.

If the user is a big building,I also prefer steam. Maybe that is because I have more experience with HHW so I have had more issues.

Solid_Fuel_Man

I've always wondered why a CI sectional boiler which is rated both steam and water has a higher output for water than steam at the same input rating. I've always assumed it was due to more wetted surface area when totally flooded with water. The two different output ratings have always led me to believe the same boiler would be less thermally efficient generating steam than simply heating water.

I really have no idea if that is true.

Jamie Hall

Is that output before derating for the pickup coefficient?

Solid_Fuel_Man

> @The Steam Whisperer said:
> Sounds like you have a mod con. If the heating curve is set tight to the actual heat loss needs, I would think the pumps would be on nearly continuously most of the winter and the boiler output would just modulate up and down. Sounds like your curve setting is high.... running a lot hotter water than necessary to maintain steady temp.

It was a summer startup in order to take these readings. My super insulated house has very low heat loss so I don't shoot for constant circulation. Solar heat gain turns the thermostat off during most every day, and slab them has significant mass to ride out many hours. I've played around with the reset curve quite a bit and find 105 degrees to be about right most days with sun, and below zero degrees F.

The Steam Whisperer

Yes, Solar gain in an efficient building throws the concept of outdoor reset and continuous circulation out the window ( pun not intended). I had a almost the same experience in my previous 1905 home that I insulated and air tightened to quite high standards ( way better than most new homes) and on typical sunny winter days in Northern Ill. the heat would shut off from about 10 until 5 each day. Lots of south and east glass. With the house unoccuppied and thermostat set for 60F our worst month gas bills for heating 3200 sq ft were about $60.00 for January and February with an on/off condensing and heat recuperative boiler ( the Dunkirk Quantum Leap), probably the highest thermal efficiency of any boiler ever made. We used standing radiators for most of the home (resized for teh current heat load). My exhaust temps ran about 15 to 20F below the return water temp due to the secondary recuperative heat exchanger that preheated the combustion air with the heat and moisture from the exhaust.

However, the impact of the type of heating system still appears to have considerable impact in very efficient homes. I had a radiant floor heating home with a simple atmospheric boiler in its own room with outdoor air. It went down one day and the homeowner flipped on the hot air furnace(they set a furnace for A/C since it was only slightly more than an air handler). The next morning everyone woke up sick because the house had turned so dry overnight. The forced air system caused so much air leakage the house dried out that quick!

mikeg2015

Love that someone pointed out that steam is a refrigerant and a team system is essentially a heat pump, without and mechanical pump.

Further, steam is not forces air, but it generates convective air movement. If you were to block air movement around the base of the radiator, output drops sharply. Actually by using covers you can reduce capacity, but still have the benefits of all the mass.

To really compare costs, you need to compare total energy used to achieve the same comfort level. Radiant system often deliver comfort at a lower ambient temperature. Force air systems also have air leaks. Similarly, steam system have heat loss in piping.

Also when comparing costs, I think you can look at life cycle cost. Ductwork will probably last 75 year, well installed steam piping maybe 150 years. Well installed on maintained stem boiler on a tight system will last 40 years or more. A forced air furnace or heat pump, maybe 20-25.

Steam boiler requires minimal power (none if standing pilot) if the power is out.

If in good condition and well installed, both can be completely silent.

RayWohlfarth

Lots of great ideas. Thank you all. I am hoping to have preliminary numbers next week

BradHotNCold

Homeowner here, following this thread, (and not pretending to fully comprehend the finer points!) I will simply say that we now live in a 1918 built home in CT with gas fired HVAC. With current heat wave, I am grateful for the A/C. But in winter I miss steam!
And hats off to all you professionals...

RayWohlfarth

@BradHotNCold I love the feeling of steam heat

Steamhead

BradHotNCold said:

Homeowner here, following this thread, (and not pretending to fully comprehend the finer points!) I will simply say that we now live in a 1918 built home in CT with gas fired HVAC. With current heat wave, I am grateful for the A/C. But in winter I miss steam!
And hats off to all you professionals...

@BradHotNCold , there are plenty of Steam Men in your area who could put steam back in your house.