We consider the standard Carnot-cycle machine, which can be thought of as having a piston moving within a cylinder, and having the following characteristics: A perfect seal, so that no atoms escape from the working fluid as the piston moves to expand or compress it. Perfect lubrication, so that there is no friction. An ideal-gas for the working fluid. Perfect thermal connection at any time either to one or to none of two reservoirs, which are at two different temperatures, with perfect thermal insulation isolating it from all other heat transfers. The piston moves back and forth repeatedly, in a cycle of alternating "isothermal" and "adiabatic" expansions and compressions, according to the PV diagram shown below: By definition, the isothermal segments (AB and CD) occur when there is perfect thermal contact between the working fluid and one of the reservoirs, so that whatever heat is needed to maintain constant temperature will flow into or out of the working fluid, from or to the reservoir. By definition, the adiabatic segments (BC and DA) occur when there is perfect thermal insulation between the working fluid and the rest of the universe, including both reservoirs, thereby preventing the flow of any heat into or out of the working fluid. The isothermal curves (but not the adiabatic curves) are hyperbolas, according to PV = nRT. The enclosed area (and therefore the mechanical work done) will depend on the two temperatures ("height") and on the amount of heat transferred, which depends in turn on the extent of the isothermal compression or expansion ("width"), during which heat must be transferred to maintain the constant temperature. We will denote the heat transferred to or from the high-temperature reservoir (during the transition between points A and B) as Qh. We will denote the heat transferred to or from the low-temperature reservoir (during the transition between points C and D) as Qc.

Given all the attention being paid to solar power these days, you might be surprised to learn that one of the most promising solutions to high energy costs isn't up in the sky but buried deep under your lawn. Superefficient geothermal heat pumps provide clean, quiet heating and cooling while cutting utility bills by up to 70 percent. "With this technology, everybody could be sitting on top of their lifetime energy supply, " says TOH plumbing and heating expert Richard Trethewey. In principle, a geothermal heat pump functions like a conventional heat pump, by using high-pressure refrigerant to capture and move heat between indoors and out. The difference is that conventional systems gather their heat—and get rid of it—through the outside air. Geothermal systems, in contrast, transfer heat through long loops of liquid-filled pipe buried in the ground. As our cave-dwelling ancestors discovered long ago, if you go far enough underground, the earth's temperature stays at a constant 50 degrees or so, no matter how hot or cold it gets outside. So while a conventional "air-source" heat pump struggles to scavenge heat from freezing winter air or to dump it into the summer swelter, its "ground-source" counterpart has the comparatively easy job of extracting and disbursing heat through the 50-degree liquid circulating in its ground loop. That's why it takes only one kilowatt-hour of electricity for a geothermal heat pump to produce nearly 12, 000 Btu of cooling or heating. (To produce the same number of Btus, a standard heat pump on a 95-degree day consumes 2.2 kilowatt-hours.) Geothermal systems are twice as efficient as the top-rated air conditioners and almost 50 percent more efficient than the best gas furnaces, all year round. Another advantage is that there's no need for a noisy outdoor fan to move air through the compressor coils. Geothermal units simply pump liquid, so they can be parked indoors, safe from the elements. Most come with 10-year warranties, but they can last much longer. In the 29 years since Jim Partin, one of the technology's earliest adopters, installed one in his Stillwater, Oklahoma, house, he's replaced only two contact switches.

A test of compressor performance was done under high temperature and pressure. • Performance of high temperature heat pump with BY-4 was studied and analyzed. • The highest heat output temperature is 110 °C with high COP of 3.61. • The maximum pressure is only 1.73 MPa when the output temperature rises up to 110 °C. A near-azeotropic refrigerant mixture named BY-4 was developed for a high temperature heat pump in the paper. The study tested the experimental performance of single-stage high temperature heat pump with BY-4 as work fluid. Under the experimental conditions of the inlet water temperature of evaporator at 50–70 °C, the outlet water temperature of condenser could reach 80–110 °C. The maximum pressure of the system was only 1.73 MPa even when the output temperature rose up to 110 °C. The experimental results showed that the COP (coefficient of performance) of heat pump was higher than 3.5 when the temperature difference between the condenser outlet water and the evaporator inlet water was less than 30 °C. Thus, BY-4 was recommended as working fluid for high temperature heat pump with a single-stage cycle due to its good comprehensive properties and excellent cycle performance. Keywords High temperature heat pump; Near-azeotropic refrigerant; Cycle performance

Triple-D Coil Cleaner is a 19oz Aerosol spray can, that is safe for homeowner use. One can will clean an entire Outdoor condesor coil and/or indoor evaporator coil, to remove energy stealing dirt, debris and soot. Manufacturer #Triple-D-AER TRIPLE-D™ is a triple active synergistic detergent system formulated to remove a broad range of soils with minimal time and effort. It will clean condensers, evaporators and Metal filters in HVAC-R systems. It contains NO toxic solvents and is nonflammable. Its unique system of surfactants, penetrants, and emulsifiers eliminates the need for expensive toxic solvent based degreasers. TRIPLE-D™ is biodegradable

This paper compares the effects of two different refrigerant flow modeling assumptions on the transient performance of vapor-compression heat pump cycles. These simulations are developed in the next-generation modeling language Modelica, which uses an acausal, equation-oriented approach to describe physical systems. The effect of the flow assumptions and specific slip ratio correlations on both the equilibrium operating point and the transient behavior of the cycle are demonstrated through these simulations. It is shown that equivalent simulations with different slip ratio correlations each have different equilibrium mass inventories, and that some aspects of the transient system behavior exhibits minor differences between the representative simulations. The effect of the software implementation on the model performance is also discussed.

A heat pump is a machine that moves heat from a cold place to a hot place. Some buildings are heated with heat pumps, also. In the winter, the heat pump moves heat from the outside to the inside. Sometimes this works better than heating with a radiator. Usually, heat flows from a hot place to a cold place, according to the second law of thermodynamics. Heat will not move from a cold place to a warmer place by itself. Because of this, a heat pump must use extra energy to move the heat. This is sort of like pumping water uphill. Most heat pumps use electric motors to provide energy. Some heat pumps use heat energy, supplied by a flame or an electric heater. Most heat pumps use a refrigeration cycle. A refrigeration cycle uses a fluid which moves through tubes and carries the heat. The fluid is called a refrigerant. During the refrigeration cycle, the refrigerant changes from a liquid to a gas and back to a liquid. The heat pump is set up so that the refrigerant gains heat from one place that will be cooled, and moves it to another place that will be warmed. A heat pump forces the refrigerant to change from a gas to a liquid. It uses a compressor to do this. Often, an electric motor drives the compressor. The compressor compresses the refrigerant, and this makes it change from a gas to a liquid. When the refrigerant changes from a gas to a liquid, it also gives up some of the heat that it has been carrying. At the other end of the cycle, the refrigerant boils again. It changes from a liquid to a gas. But it needs heat to do this. When it takes up heat from its surroundings, it cools them down. So where the refrigerant is changing from a liquid to a gas, it feels cooler.

Video: Paul Ledman's net-zero apartment building in Portland, Maine which uses 100% solar for heating and cooling and will never need fossil fuel inputs. Reduce your reliance on dirty, expensive oil heat with efficient heat pump heating technology. Modern ductless, mini-split air source heat pumps (ASHPs) run 2-3x as efficiently as traditional 'resistive' electric heat, making the cost to run the units equivalent to . Simultaneously, they provide air conditioning using half the energy as traditional window or central air conditioning systems. Best yet - by installing a solar electric array to power the electric consumption of the heat pumps, you effectively have a solar space heating system. Your solar array will generate credits in the summertime (when it is sunniest) which allow you to run the heat pumps in the wintertime (when it is coldest). Your system will effortlessly generate all the 'fuel' it ever needs from clean, abundant sunshine! 0-down, 2.99% financing is available through ReVision's Own Your Power solar loan program. Cost of Heating Comparison Heat pumps are less than half the cost to operate vs. the equivalent oil or propane system on a per BTU basis. This chart gives you a quick breakdown of relative costs. Fuel Source Cost per Unit Cost per Million BTUs Cost to Heat Typical Home Electric Baseboard Million BTUs Electric Baseboard $0.14 / kWh $44 $4, 489 Propane $2.73 / gallon $40 $3, 873 Heating Oil $2.70 / gallon $25 $2.14 / kWh , 489 Propane .73 / gallon , 873 Heating Oil .70 / gallon , 421 Heat Pump $0.14 / kWh $18 $1, 706 Heat Pump with Solar $0.09 / kWh $11 $1, 023 Based on fuel data and pricing from: Maine Energy Office. Assumes typical oil boiler operating at 65% efficiency, propane at 85% efficiency, resistive electric at 95% efficiency and heat pump at 250% efficiency (COP of 2.5). Solar PV kilowatt-hour cost of 8.5cents per kilowatt-hour based on typical pricing economics of a 4kw + system. How Air Source Heat Pumps Work Outdoor Mitsubishi heat pump unit, Greene, Maine. Indoor Mitsubishi heat pump unit, Greene, Maine. Air source heat pumps extract heat from the outside air using a reverse refrigeration cycle (imagine if you took a window air conditioner and flipped it around). By extracting heat from the the outside air and moving it inside, rather than directly heating the indoor air, the heat pump runs 2-3 times more efficiently than an electric baseboard heater. This is commonly referred to as a coefficient of performance (COP) of 2-3.

So, you've got a heating and cooling system in your home. There's a metal box outside that makes noise, and you control it with the thermostat on the wall. Can you tell me right now whether it's a heat pump or just an air conditioner? This is a really important question to be able to answer when you're talking to an engineer or contractor at a cocktail party. The diference between the two is simple. An air conditioner moves heat from inside your home to outside in the summer. A heat pump does that and also moves heat from outside to inside in winter. Really, what we call an air conditioner is just as much a heat pump as the device that owns the heat pump name. It's just that the air conditioner pumps heat in only one direction. (Regrigerators and dehumidifiers do the same thing pretty much.) Now, back to my question, do you or don't you know what you have? If you don't, here's your opportunity to do a little snooping and find out. Here are three ways: Go outside and find the model number of the metal noisemaker (aka the condensing unit). Type that number into the search box in your browser and see what the all-wise Internets tell you about it. You might need to type in the brand name, too. That search should get you the answer. Go outside and peer down through the grill on top of the condensing unit. If you see a horizontal brass pipe similar to the one shown in the photo at right, you've got a heat pump. That piece is called the reversing valve, and it's what allows a heat pump to pump heat in both directions. Note: If you look down in there and don't see one, that doesn't mean it's not a heat pump. Sometimes they're hidden behind the access panel outside the coil, as was the case for the one in the photo. Go inside and set your thermostat to heat. Adjust the temperature setting until the heat comes on in your home. Now go outside and see if the condensing unit is making noise and blowing air. If it is, you have a heat pump. ( Note: This doesn't always work, but something else about the thermostat tells you the answer, too. See first comment below. ) Now that you know what you have, you'll never be embarrassed at cocktail parties again! When that contractor starts telling you about TXVs, subcooling, and superheat, or the engineer starts talking about mean radiant temperature, comfort, naked people, and building science (you have to watch out for those engineers!), you'll be ready. I suggest carrying a photo of your reversing valve with you at all times. I certainly do. I keep it right next to my card with 101 digits of pi and the photo of my pride and joy.

Abstract: The conventional control paradigm for a heat pump with a less efficient auxiliary heating element is to keep its temperature set point constant during the day. This constant temperature set point ensures that the heat pump operates in its more efficient heat-pump mode and minimizes the risk of activating the less efficient auxiliary heating element. As an alternative to a constant set-point strategy, this paper proposes a learning agent for a thermostat with a set-back strategy. This set-back strategy relaxes the set-point temperature during convenient moments, e.g. when the occupants are not at home. Finding an optimal set-back strategy requires solving a sequential decision-making process under uncertainty, which presents two challenges. A first challenge is that for most residential buildings a description of the thermal characteristics of the building is unavailable and challenging to obtain. A second challenge is that the relevant information on the state, i.e. the building envelope, cannot be measured by the learning agent. In order to overcome these two challenges, our paper proposes an auto-encoder coupled with a batch reinforcement learning technique. The proposed approach is validated for two building types with different thermal characteristics for heating in the winter and cooling in the summer. The simulation results indicate that the proposed learning agent can reduce the energy consumption by 4-9% during 100 winter days and by 9-11% during 80 summer days compared to the conventional constant set-point strategy Submission history From: Frederik Ruelens [view email]

Occasionally I get asked if it's OK to put the condensing unit for an air conditioner or heat pump in a garage or other room that's a buffer space. The thinking is that since the temperature may not be as hot in summer or as cold in winter, the system will operate more efficiently. I just saw yesterday that this same question came up in a column in Home Power magazine, so I thought this would be a good time to cover this issue (once and for all?) here. The answer is no. In fact, the answer is an emphatic NO. Here's why: The way an 'air source' heat pump or air conditioner works is that it exchanges heat with the air surrounding the condenser. In summer, it dumps heat into that air. In winter, it absorbs heat from that air. When the condenser sits outdoors, it's connected to a mass of air that's practically infinite. In other words, no matter how much heat that unit dumps outside, it's not going to change the outdoor temperature. If you put the condenser in a garage, attic (as shown above), or other space, it's now connected to a finite mass of air. As it dumps heat into that air in summer, the temperature in the room will rise. As it pulls heat from it in winter, the temperature will drop. The smaller that room, the more temperature change you'll get. What do you think happens to the efficiency and capacity of an air conditioner when it has to dump its heat into hotter air? It drops. What happens when the air gets too hot? The condenser may not be able to do its job - condensing the refrigerant so that it all becomes a liquid again. The refrigerant goes to the evaporator coil hotter and wetter and at higher pressure. That's a recipe for failure. Condensing unit in an attic?! I have no idea why anyone would put an air conditioner in an attic, as shown above, but the second photo of that unit shows another problem. That system not only is working with a smaller, hotter volume of air, but it's sucking blown insulation up against the coil, reducing the air flow. I guess they wanted to make sure that system failed as quickly as possible. Even in a cold climate where you don't use the system for cooling, you can't do this. Not only is there not enough air, but if the temperature is higher, it's at least partially due to heat loss from the house. A better building enclosure is a much more practical way to keep the heat in your home in winter. 11 condensers in one small room The photo above is from a Facebook page called . They show lots of good photos of HVAC gone wrong. If you think I post some ugly stuff here, take a look at their page. They posted the photo above yesterday. The caption said that in addition to the 6 condensers you see here, another 5 were in the room, too. That's 11 condensers in a room so small that the widest angle photo he could get shows only about a 10 foot section. Wow! Not only is there a small volume of air, but you have 11 condensers fighting over the little that's there. Yeah, they've got louvers connecting it to more air (a parking deck? outdoors?), but that's not sufficient.