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Power cost of idle electric water heater
I recently installed an electric water heater to service a guest bedroom
located far from the central water heater. Since water will be drawn from this heater only when guests are visiting, I plan to leave it turned off to save power. But before shutting it down, I decided to take some measurements and calculate how much it costs to run an idle water heater. The water heater is an electric GE Smar****er 40 gallon, “lowboy” (squat) unit. The plate on the unit says it draws 4500 watts, but my measurements show that it actually draws about 4320 watts (18 amps at 240 volts). The EPA estimated annual cost of operation is $401. I used a Supco model DLAC recording clamp-on ammeter to record power (amperage) over a 3 day interval. During the same period, I used a Supco model DLT recording thermometer to record the ambient air temperature in the crawl space where the water heater is located. Here is a summary of my measurements: Monitored interval: 3 days Power draw when heating element is on: 4320 watts (18 amps at 240 volts) Duty cycle when heater is running: 0.0161 (1.61%) Average power used (heating watts times duty cycle): 69.55 watts Temperature of hot water delivered: 114 degrees F. Average temperature in crawl space during measurement period: 61 degrees F. Temperature rise for water: 53 degrees F (114 - 61) When the heater is on, it draws 4320 watts. However, the duty cycle (proportion of time heating) is only 0.0161 (1.61%), so the average power drawn is 4320*0.0161=69.55 watts. (On average, the heating element is on 23 minutes/day.) An average power usage of 69.55 watts over 24 hours works out to 1.669 KWH (kilo-watt hours) per day. The EPA average national power rate is 8 cents per KWH. So, using the EPA power rate, the cost of keeping the idle water heater hot is 13.35 cents/day or $4.00/month or $48.73/year. Here in Tennessee, we enjoy relatively cheap TVA power which costs 5.6 cents/KWH. Using that rate, the energy cost is 9.35 cents/day, $2.80/month or $34.13/year. The EPA estimated annual cost of operation is $401 (assuming 8 cents/KWH). So the idle heat-loss cost of $48.73/year is about 12% of the total cost. If you adapt these figures for another location, remember that the cost is directly proportional to the temperature difference between the hot water and the surrounding room temperature, and you must adjust for your KWH power cost. Phil Sherrod (phil.sherrod 'at' sandh.com) Index: power, energy, cost, water heater, waterheater, KWH, energy use, cost of hot water, hot water cost, efficiency, power rate, electric water heater, |
Power cost of idle electric water heater
Phil Sherrod wrote:
I recently installed an electric water heater to service a guest bedroom located far from the central water heater. Since water will be drawn from this heater only when guests are visiting, I plan to leave it turned off to save power. But before shutting it down, I decided to take some measurements and calculate how much it costs to run an idle water heater. The water heater is an electric GE Smar****er 40 gallon, “lowboy” (squat) unit. The plate on the unit says it draws 4500 watts, but my measurements show that it actually draws about 4320 watts (18 amps at 240 volts). The EPA estimated annual cost of operation is $401. I used a Supco model DLAC recording clamp-on ammeter to record power (amperage) over a 3 day interval. During the same period, I used a Supco model DLT recording thermometer to record the ambient air temperature in the crawl space where the water heater is located. Here is a summary of my measurements: Monitored interval: 3 days Power draw when heating element is on: 4320 watts (18 amps at 240 volts) Duty cycle when heater is running: 0.0161 (1.61%) Average power used (heating watts times duty cycle): 69.55 watts Temperature of hot water delivered: 114 degrees F. Average temperature in crawl space during measurement period: 61 degrees F. Temperature rise for water: 53 degrees F (114 - 61) When the heater is on, it draws 4320 watts. However, the duty cycle (proportion of time heating) is only 0.0161 (1.61%), so the average power drawn is 4320*0.0161=69.55 watts. (On average, the heating element is on 23 minutes/day.) An average power usage of 69.55 watts over 24 hours works out to 1.669 KWH (kilo-watt hours) per day. The EPA average national power rate is 8 cents per KWH. So, using the EPA power rate, the cost of keeping the idle water heater hot is 13.35 cents/day or $4.00/month or $48.73/year. Here in Tennessee, we enjoy relatively cheap TVA power which costs 5.6 cents/KWH. Using that rate, the energy cost is 9.35 cents/day, $2.80/month or $34.13/year. The EPA estimated annual cost of operation is $401 (assuming 8 cents/KWH). So the idle heat-loss cost of $48.73/year is about 12% of the total cost. If you adapt these figures for another location, remember that the cost is directly proportional to the temperature difference between the hot water and the surrounding room temperature, and you must adjust for your KWH power cost. Phil Sherrod (phil.sherrod 'at' sandh.com) Thanks, Phil. Interesting. Depending on ease of access, you might consider a low temp setting when not in use, turning it up when needed. Some new models have settings for vacation, energy save, peak demand, and normal. Don't know if it's true but I've heard recommendations against turning them off completely unless for very extended periods. Marv |
Power cost of idle electric water heater
Did you consider a demand heater? Whould seem to make sense
for occational type use. Doug s/v Callista "Phil Sherrod" wrote in message ... I recently installed an electric water heater to service a guest bedroom located far from the central water heater. Since water will be drawn from this heater only when guests are visiting, I plan to leave it turned off to save power. But before shutting it down, I decided to take some measurements and calculate how much it costs to run an idle water heater. The water heater is an electric GE Smar****er 40 gallon, "lowboy" (squat) unit. The plate on the unit says it draws 4500 watts, but my measurements show that it actually draws about 4320 watts (18 amps at 240 volts). The EPA estimated annual cost of operation is $401. I used a Supco model DLAC recording clamp-on ammeter to record power (amperage) over a 3 day interval. During the same period, I used a Supco model DLT recording thermometer to record the ambient air temperature in the crawl space where the water heater is located. Here is a summary of my measurements: Monitored interval: 3 days Power draw when heating element is on: 4320 watts (18 amps at 240 volts) Duty cycle when heater is running: 0.0161 (1.61%) Average power used (heating watts times duty cycle): 69.55 watts Temperature of hot water delivered: 114 degrees F. Average temperature in crawl space during measurement period: 61 degrees F. Temperature rise for water: 53 degrees F (114 - 61) When the heater is on, it draws 4320 watts. However, the duty cycle (proportion of time heating) is only 0.0161 (1.61%), so the average power drawn is 4320*0.0161=69.55 watts. (On average, the heating element is on 23 minutes/day.) An average power usage of 69.55 watts over 24 hours works out to 1.669 KWH (kilo-watt hours) per day. The EPA average national power rate is 8 cents per KWH. So, using the EPA power rate, the cost of keeping the idle water heater hot is 13.35 cents/day or $4.00/month or $48.73/year. Here in Tennessee, we enjoy relatively cheap TVA power which costs 5.6 cents/KWH. Using that rate, the energy cost is 9.35 cents/day, $2.80/month or $34.13/year. The EPA estimated annual cost of operation is $401 (assuming 8 cents/KWH). So the idle heat-loss cost of $48.73/year is about 12% of the total cost. If you adapt these figures for another location, remember that the cost is directly proportional to the temperature difference between the hot water and the surrounding room temperature, and you must adjust for your KWH power cost. Phil Sherrod (phil.sherrod 'at' sandh.com) Index: power, energy, cost, water heater, waterheater, KWH, energy use, cost of hot water, hot water cost, efficiency, power rate, electric water heater, |
Power cost of idle electric water heater
On 30-Mar-2004, "Doug Dotson" wrote: Did you consider a demand heater? Whould seem to make sense for occational type use. Yes, but there was no way to justify it. Since the maximum savings with my power rate would be $3/month it would take a LONG time to offset the hundreds of dollars in extra cost. Plus, I can easily switch off the circuit breaker for the weeks or months when we don't need the heater. |
Power cost of idle electric water heater
On Wed, 31 Mar 2004 00:53:00 GMT, "Phil Sherrod"
wrote: On 30-Mar-2004, "Doug Dotson" wrote: Did you consider a demand heater? Whould seem to make sense for occational type use. Yes, but there was no way to justify it. Since the maximum savings with my power rate would be $3/month it would take a LONG time to offset the hundreds of dollars in extra cost. Plus, I can easily switch off the circuit breaker for the weeks or months when we don't need the heater. If you live in a humid area I'd recommend not switching the heater off. The outside of the tank is still just steel with the fiberglass insulation in contact. When the humidity is high humidity will condense on the tank surface and set up rust. The fiberglass will help hold the water in there. BTDT at my summer cabin in the Smokey mountains. Lost 3 water heaters in short order to outside-the-tank rust before I gave in and left it energized all the time. Current heater's been there for 10+ years. John --- John De Armond http://bellsouthpwp.net/j/o/johngd/ Cleveland, Occupied TN |
Power cost of idle electric water heater
On 31-Mar-2004, "Roland Paterson-Jones" wrote: Mmm, hot water delivered is 114F, that's 45C, hardly luke-warm! We have to take the rest of the measurements with a pinch of salt then. As you know, heat loss is proportional to the temperature delta. How about a realistic scenario. OK, let's bump the temperature up to 125F. That's a temperature differential of 64F. That means the heat loss and cost increases by a factor of 64/51. The average heat loss cost at 114F is $4/month, so at 125F it will be $5.02. (4*64/51) But, of course, don't forget that many people keep their water heaters in areas that are warmer than 61F, so the temperature differential may be lower than mine. The main issue with electric water heaters, as far as I'm concerned, is that the Carnot-limited power source wastes at least 60% of the fuel source heat to the local rivers and dams, for you to take the (optimistic) 40% and convert it back to heat. I have absolutely no control over that nor was my study directed at that issue. Your case study is flawed, and you lack appreciation of the big picture. I never claimed to be presenting either a study or a solution to the "big picture" of energy usage. My study was simply to measure the actual heat loss energy for one water heater in a known environment. As shown above, you can adapt the figures to other situations. |
Power cost of idle electric water heater
On 31-Mar-2004, "Roland Paterson-Jones" wrote: Mmm, hot water delivered is 114F, that's 45C, hardly luke-warm! We have to take the rest of the measurements with a pinch of salt then. As you know, heat loss is proportional to the temperature delta. How about a realistic scenario. OK, let's bump the temperature up to 125F. That's a temperature differential of 64F. That means the heat loss and cost increases by a factor of 64/51. The average heat loss cost at 114F is $4/month, so at 125F it will be $5.02. (4*64/51) But, of course, don't forget that many people keep their water heaters in areas that are warmer than 61F, so the temperature differential may be lower than mine. The main issue with electric water heaters, as far as I'm concerned, is that the Carnot-limited power source wastes at least 60% of the fuel source heat to the local rivers and dams, for you to take the (optimistic) 40% and convert it back to heat. I have absolutely no control over that nor was my study directed at that issue. Your case study is flawed, and you lack appreciation of the big picture. I never claimed to be presenting either a study or a solution to the "big picture" of energy usage. My study was simply to measure the actual heat loss energy for one water heater in a known environment. As shown above, you can adapt the figures to other situations. |
Power cost of idle electric water heater
On Thu, 1 Apr 2004 01:04:20 GMT, "Phil Sherrod"
wrote: The main issue with electric water heaters, as far as I'm concerned, is that the Carnot-limited power source wastes at least 60% of the fuel source heat to the local rivers and dams, for you to take the (optimistic) 40% and convert it back to heat. I have absolutely no control over that nor was my study directed at that issue. Your case study is flawed, and you lack appreciation of the big picture. I never claimed to be presenting either a study or a solution to the "big picture" of energy usage. My study was simply to measure the actual heat loss energy for one water heater in a known environment. As shown above, you can adapt the figures to other situations. Phil, Just ignore Roland. He just likes to hear himself type and throw out fancy terms. Doesn't have a clue. Your measurements were right on target. Even the temperature selected. The water heater I recently installed in one of my cabins came from the Home Depot with the 'stats set at 115 deg F. Probably the lawyers at work again. I bet just about nobody changes that setting. Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John --- John De Armond http://bellsouthpwp.net/j/o/johngd/ Cleveland, Occupied TN |
Power cost of idle electric water heater
On Thu, 1 Apr 2004 01:04:20 GMT, "Phil Sherrod"
wrote: The main issue with electric water heaters, as far as I'm concerned, is that the Carnot-limited power source wastes at least 60% of the fuel source heat to the local rivers and dams, for you to take the (optimistic) 40% and convert it back to heat. I have absolutely no control over that nor was my study directed at that issue. Your case study is flawed, and you lack appreciation of the big picture. I never claimed to be presenting either a study or a solution to the "big picture" of energy usage. My study was simply to measure the actual heat loss energy for one water heater in a known environment. As shown above, you can adapt the figures to other situations. Phil, Just ignore Roland. He just likes to hear himself type and throw out fancy terms. Doesn't have a clue. Your measurements were right on target. Even the temperature selected. The water heater I recently installed in one of my cabins came from the Home Depot with the 'stats set at 115 deg F. Probably the lawyers at work again. I bet just about nobody changes that setting. Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John --- John De Armond http://bellsouthpwp.net/j/o/johngd/ Cleveland, Occupied TN |
Power cost of idle electric water heater
On 31-Mar-2004, Neon John wrote: Just ignore Roland. He just likes to hear himself type and throw out fancy terms. Doesn't have a clue. Your measurements were right on target. Even the temperature selected. The water heater I recently installed in one of my cabins came from the Home Depot with the 'stats set at 115 deg F. Probably the lawyers at work again. I bet just about nobody changes that setting. Even Roland's appreciation of the "big picture" is incorrect. Yes, Roland's "big picture" is incorrect. The problem with European environmentalists like him is that they are cultural imperialists: They want to impose their standard of living, cars, energy generation, insulation, house sizes, lighting and room temperatures on all other cultures. They even have standards for family size. I could care less whether he rides a bicycle or drives a Mercedes, but it really bothers him that I drive a SUV and have 200 watts of light in my office. But what's worse is that if he had the opportunity, he would impose his political/environmental/social policy on the whole world. "Liberals" are only tolerant of other liberals; they are dogmatic and unwilling to accept those who prefer different lifestyles. |
Power cost of idle electric water heater
On 31-Mar-2004, Neon John wrote: Just ignore Roland. He just likes to hear himself type and throw out fancy terms. Doesn't have a clue. Your measurements were right on target. Even the temperature selected. The water heater I recently installed in one of my cabins came from the Home Depot with the 'stats set at 115 deg F. Probably the lawyers at work again. I bet just about nobody changes that setting. Even Roland's appreciation of the "big picture" is incorrect. Yes, Roland's "big picture" is incorrect. The problem with European environmentalists like him is that they are cultural imperialists: They want to impose their standard of living, cars, energy generation, insulation, house sizes, lighting and room temperatures on all other cultures. They even have standards for family size. I could care less whether he rides a bicycle or drives a Mercedes, but it really bothers him that I drive a SUV and have 200 watts of light in my office. But what's worse is that if he had the opportunity, he would impose his political/environmental/social policy on the whole world. "Liberals" are only tolerant of other liberals; they are dogmatic and unwilling to accept those who prefer different lifestyles. |
OT: Supercritical Fossil Plants
In article ,
Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. -- Jere Lull Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD) Xan's Pages: http://members.dca.net/jerelull/X-Main.html Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/ |
OT: Supercritical Fossil Plants
In article ,
Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. -- Jere Lull Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD) Xan's Pages: http://members.dca.net/jerelull/X-Main.html Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/ |
Power cost of idle electric water heater
The EPA average national power rate is 8 cents per KWH. So, using the EPA
power rate, the cost of keeping the idle water heater hot is 13.35 cents/day or $4.00/month or $48.73/year. Phil, Thanks for the complete info. I'm MORE than willing to pay $49/yr so I can have hot water when I turn the handle. The losses must be a bit larger with a 6 gal RV water heater but it is sure nice to have hot water! Based on your data it'd probably take quite a while to recover the cost of an "instantaneous" heater. I'll wait 'til my old fashioned one fails before looking at greater efficiency. I recently did some cold weather camping & was surpised at how little I missed the hot water. I guess the new detergents are much better than soap for getting things clean with cold water. Thanks again and please continue to report useful data. Ignore those who turn every posting into some kind of ideological argument (they are ideots!) |
Power cost of idle electric water heater
The EPA average national power rate is 8 cents per KWH. So, using the EPA
power rate, the cost of keeping the idle water heater hot is 13.35 cents/day or $4.00/month or $48.73/year. Phil, Thanks for the complete info. I'm MORE than willing to pay $49/yr so I can have hot water when I turn the handle. The losses must be a bit larger with a 6 gal RV water heater but it is sure nice to have hot water! Based on your data it'd probably take quite a while to recover the cost of an "instantaneous" heater. I'll wait 'til my old fashioned one fails before looking at greater efficiency. I recently did some cold weather camping & was surpised at how little I missed the hot water. I guess the new detergents are much better than soap for getting things clean with cold water. Thanks again and please continue to report useful data. Ignore those who turn every posting into some kind of ideological argument (they are ideots!) |
Supercritical Fossil Plants
"Jere Lull" wrote in message ... In article , Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. Indian Point I (long shutdown now) was a nuke that used the reactor to make saturated steam, then used an oil-fired superheater to superheat the steam. Not sure how hot it ran, but pressure was only about 1000 psi (due to the limits of the nuke's steam-generator). In recent past, the industry has been going for combined-cycle gas-turbine. Less pollution controls needed and overall cycle efficiencies running close to 60%. But this has raised demand on natural gas, so that price has started to climb and things are shifting once again. daestrom |
Supercritical Fossil Plants
"Jere Lull" wrote in message ... In article , Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. Indian Point I (long shutdown now) was a nuke that used the reactor to make saturated steam, then used an oil-fired superheater to superheat the steam. Not sure how hot it ran, but pressure was only about 1000 psi (due to the limits of the nuke's steam-generator). In recent past, the industry has been going for combined-cycle gas-turbine. Less pollution controls needed and overall cycle efficiencies running close to 60%. But this has raised demand on natural gas, so that price has started to climb and things are shifting once again. daestrom |
Supercritical Fossil Plants
Indian Point was an efficiency disaster from the start-up. Probably
due to the inability of the main turbine condensers from operating down to 1" hg. absolute. No one ever found out why the plants thermo cycle was so way 'out of whack'. Suggestions were posed but never proved that the condensation on the condenser tubes was not film-wise condensation but some sort of 'wierd' drop-wise or mixture condensation ..... and no one ever found out why. In article , daestrom wrote: "Jere Lull" wrote in message ... In article , Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. Indian Point I (long shutdown now) was a nuke that used the reactor to make saturated steam, then used an oil-fired superheater to superheat the steam. Not sure how hot it ran, but pressure was only about 1000 psi (due to the limits of the nuke's steam-generator). In recent past, the industry has been going for combined-cycle gas-turbine. Less pollution controls needed and overall cycle efficiencies running close to 60%. But this has raised demand on natural gas, so that price has started to climb and things are shifting once again. daestrom |
Supercritical Fossil Plants
Indian Point was an efficiency disaster from the start-up. Probably
due to the inability of the main turbine condensers from operating down to 1" hg. absolute. No one ever found out why the plants thermo cycle was so way 'out of whack'. Suggestions were posed but never proved that the condensation on the condenser tubes was not film-wise condensation but some sort of 'wierd' drop-wise or mixture condensation ..... and no one ever found out why. In article , daestrom wrote: "Jere Lull" wrote in message ... In article , Neon John wrote: Even Roland's appreciation of the "big picture" is incorrect. Modern supercritcal fossil plants achieve overall efficiencies in the 50% range. Even the good old nuke are in the high 30s. The Sequoyah Nuclear Plant where I worked for about 10 years recently replaced the steam generators. The improved design plus some plant upgrades pushed the efficiency to 38% and a fraction, something that spawned a small staff party. Oh, and BTW, Roland, the waste heat goes up the cooling tower stacks and not into the lake, at least not to any significant extent. Much to the chagrin of local fishermen who discovered that the warm water (pre-cooling towers) spawned great fish growth and fishing conditions. John De Armond Depending on *how* it's measured, efficiency can be higher. Back in '70, I worked as a co-op at the Eddystone plant (Philly area), then arguably the most efficient plant in the world -- only the USSR supposedly had a better one. Steam started at 4,999.5 psi according the gauge, ended in partial vacuum. They burned (actually closer to exploded) 1-200 tons of coal an hour and we STILL needed heaters in the "basement" labs in the winter. [yes, we had walls ;-)] They only used the gas turbines (jet engines) in the yard when absolutely necessary, because their efficiency was so low. By each measure, efficiency was pretty high. But are they making plants like that any more? When they built units 3 & 4, they went back to a "mere" 1-2000 psi. AFAIK, only one supercritical production nuke was built: Peachbottom. Indian Point I (long shutdown now) was a nuke that used the reactor to make saturated steam, then used an oil-fired superheater to superheat the steam. Not sure how hot it ran, but pressure was only about 1000 psi (due to the limits of the nuke's steam-generator). In recent past, the industry has been going for combined-cycle gas-turbine. Less pollution controls needed and overall cycle efficiencies running close to 60%. But this has raised demand on natural gas, so that price has started to climb and things are shifting once again. daestrom |
Supercritical Fossil Plants
"Rich Hampel" wrote in message ... Indian Point was an efficiency disaster from the start-up. Probably due to the inability of the main turbine condensers from operating down to 1" hg. absolute. No one ever found out why the plants thermo cycle was so way 'out of whack'. Suggestions were posed but never proved that the condensation on the condenser tubes was not film-wise condensation but some sort of 'wierd' drop-wise or mixture condensation .... and no one ever found out why. Actually, what you suggest might be backwards. 'drop-wise' condensation is a much better heat-transfer mechanism than film. The two major performance issues on the steam side of condensers is the thickness of the film through which heat must be transferred in order to get to the metal tube, and the amount of non-condensibles that accumulate against the film surface (even trace amounts develop a film through which the vapor must diffuse to reach the film). I have a good book at work ("Heat-Transfer", can't recall the author/publisher from here) that has a couple of good chapters on condensing mechanisms. Although somewhat dated (circa ~1990), it discusses that the 'Holy Grail' of condenser performance is to develop surfaces for promoting stable 'drop-wise' condensation. No film against tube surface means heat transfer coefficients can be on the order of 3X to 8X better. The non-condensables problem has been well managed for many years with 'dry suction pipes' and other design features. I know IP One has been shutdown for a long time, didn't know it had an abysmal performance problem. Just pointed out that it had a unique combination of nuc and fossil fuels. It might be interesting to pour over the old operating logs/data and apply the modern tools of station thermo performance to see where things were NQR (not quite right). Of course, some engineer may have found the problem back then, but the cost of fixing it after the plant was already built may have been prohibitive. If the design had hoped to achieve drop-wise condensation in the condenser (by using some special treatment on the tube surface) but was not able to, that would have required reverting back to a larger, film-wise surface condenser. The cost of putting in a larger condenser and ripping apart the turbine deck and all to do so would probably be reason enough to lock the door and walk away. daestrom |
Supercritical Fossil Plants
"Rich Hampel" wrote in message ... Indian Point was an efficiency disaster from the start-up. Probably due to the inability of the main turbine condensers from operating down to 1" hg. absolute. No one ever found out why the plants thermo cycle was so way 'out of whack'. Suggestions were posed but never proved that the condensation on the condenser tubes was not film-wise condensation but some sort of 'wierd' drop-wise or mixture condensation .... and no one ever found out why. Actually, what you suggest might be backwards. 'drop-wise' condensation is a much better heat-transfer mechanism than film. The two major performance issues on the steam side of condensers is the thickness of the film through which heat must be transferred in order to get to the metal tube, and the amount of non-condensibles that accumulate against the film surface (even trace amounts develop a film through which the vapor must diffuse to reach the film). I have a good book at work ("Heat-Transfer", can't recall the author/publisher from here) that has a couple of good chapters on condensing mechanisms. Although somewhat dated (circa ~1990), it discusses that the 'Holy Grail' of condenser performance is to develop surfaces for promoting stable 'drop-wise' condensation. No film against tube surface means heat transfer coefficients can be on the order of 3X to 8X better. The non-condensables problem has been well managed for many years with 'dry suction pipes' and other design features. I know IP One has been shutdown for a long time, didn't know it had an abysmal performance problem. Just pointed out that it had a unique combination of nuc and fossil fuels. It might be interesting to pour over the old operating logs/data and apply the modern tools of station thermo performance to see where things were NQR (not quite right). Of course, some engineer may have found the problem back then, but the cost of fixing it after the plant was already built may have been prohibitive. If the design had hoped to achieve drop-wise condensation in the condenser (by using some special treatment on the tube surface) but was not able to, that would have required reverting back to a larger, film-wise surface condenser. The cost of putting in a larger condenser and ripping apart the turbine deck and all to do so would probably be reason enough to lock the door and walk away. daestrom |
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