In my house I have 3 small air conditioning systems running at 8000 BTU/hour each. I would like to power them with solar energy. I found that I would have to generate: 3.41 BTU/hr = 1 Watt 8000 BTU/hr = 2346 Watts That means to power the 3 units for 4 hours/day, I would need (2346 Watts* 4 hours/day * 3) = 28152 W*hours/day, or approximately 30 kWh/day. I checked that in my region, I have 7 hours of sun each day. So to generate 30kWh/day, I will need something like 5kWh/hour = 5000 Watts. Are these calculations right? Going further, I'm able to generate now (i have 4 * 250 watts solar panels) 1kW, but I generate it 7 days per week, and I use the air conditioners, maybe 2 times/week. Thinking in this scenario, I don't have to be so concerned about how much energy can I generate hourly/daily, but weekly right? Another important point here is the batteries where I will store the generated energy right? Any suggestion which kind of batteries set should I use?

Actually your AC is much more efficient than that because it is a heat pump, not a direct conversion of electrical watts in to BTU of heat moved per hour. If you know your SEER rating, you can just divide the BTU/h by SEER to get Watts. An SEER of 10 is very common so that would mean each AC needs 800 W to move 8000 BTU per hour. BTW, it's good to keep your units straight between energy and power (which is the rate that energy is being used).how do commercial ac units work Watt-hours and BTU are energy.ac unit running but no air coming out Watts and BTU/hour are power.best air conditioner package unit And your AC is not 8000 BTU, it's 8000 BTU/hour. Cannot answer #1 or #3 but WRT #2, with intermittent usage you want enough storage to last you approximately 2x to 3x your longest period of A/C use without sufficient light to generate the necessary power.

Usually this will be at night - but depending on where you live it also might be on an extended period of hot, rainy days. For instance, recently in Maryland we had over a week of 80-90 degree days with POURING rain and 100% humidity. Just wondering - instead of going with batteries, can you go solar-on-grid, where your excess energy goes into the grid (and you get paid for it) and when your solar isn't generating enough, you can draw from the grid?Browse other questions tagged air-conditioning solar-panels alternative-energy or ask your own question.Can I save money by getting a window air conditioner and using my central air less? August 8, 2012   Subscribe Will turning up the thermostat on my central air and buying a window AC unit for the one room I use the most make a significant difference in my electric bill? This is hopefully a simple question, but I'm not confident that my assumptions are correct. I recently bought a house, it's a 2-story that's about 1750 square feet, located in Michigan USA.

The house has a central air unit that looks very very old, but still functions well. The thermostat in the house is on the ground floor, and I've kept it set to about 70 degrees Fahrenheit when I'm home, since the upper floor tends to be at least 7-8 degrees warmer than the ground floor, and I spend more of my time upstairs. I am currently the only person living here. The outside temperatures during July were generally in the 90s, occasionally in the 100s. I knew that cooling a 1750 square foot house was going to cost more than cooling my old 1-bedroom apartment. But I was surprised by just how much more. My electric bill last month was $260, twice the highest amount I ever paid while living in an apartment! I'm guessing that the AC is the main difference between the bills at these two places, since everything else I own is more or less the same, and is getting the same amount of use (same computers and TVs, comparable refrigerator, etc). I'm trying to figure out how to save money on my electric bill while at the same time cooling my upstairs bedroom/office more effectively.

I'm thinking I could put a window air conditioner in my bedroom upstairs, and then turn the downstairs thermostat up to 78 or so. My question is though: Would this actually save me any money? I'd still be using the central air to cool the rest of the house, just not as much. Would the difference be enough to justify the cost of the window unit? In particular, I was looking at purchasing the Frigidaire FRA086AT7, which costs $200. To justify that expense in the short-term, I'd hope to save at least $40/month on my electric bill by using this strategy. I really don't have a good feel for that the impact on my energy usage would be. Especially since I don't intend to turn the central air off altogether. If this wouldn't be an effective money-saver, do you have any other suggestions? If you have any hard data, or you've done something like this and can tell me about your experience, I'd love to hear it! Heat recovery ventilation (HRV), also known as mechanical ventilation heat recovery (MVHR), is an energy recovery ventilation system using equipment known as a heat recovery ventilator, heat exchanger, air exchanger, or air-to-air heat exchanger which employs a cross flow or counter-flow heat exchanger (countercurrent heat exchange) between the inbound and outbound air flow.

[1] HRV provides fresh air and improved climate control, while also saving energy by reducing heating (and cooling) requirements for many applications including vehicles. Energy recovery ventilators (ERVs) are closely related, however ERVs also transfer the humidity level of the exhaust air to the intake air. As building efficiency is improved with insulation and weather stripping, buildings are intentionally made more airtight, and consequently less well ventilated. Since all buildings require a source of fresh air, the need for HRVs has become obvious. While opening a window does provide ventilation, the building's heat and humidity will then be lost in the winter and gained in the summer, both of which are undesirable for the indoor climate and for energy efficiency, since the building's heating, ventilating/ventilation, and air conditioning (HVAC) systems must compensate. HRV introduces fresh air to a building and improves climate control, whilst promoting efficient energy use.

UK building regulations require one air change every two hours (0.5 ACH). With traditional extract-only ventilation that means a house boiler would need to warm up a house-full of cold air 12 times a day. HRVs and ERVs can be stand-alone devices that operate independently, or they can be built-in, or added to existing HVAC systems. For a small building in which nearly every room has an exterior wall, then the HRV/ERV device can be small and provide ventilation for a single room. A larger building would require either many small units, or a large central unit. The only requirements for the building are an air supply, either directly from an exterior wall or ducted to one, and an energy supply for air circulation, such as wind energy or electricity for fans and electronic control system. When used with 'central' HVAC systems, then the system would be of the 'forced-air' type. Types of Recuperator air-to-air heat exchangers. There are a number of types of air-to-air heat exchanger that can be used in HRV devices:

The air coming into the heat exchanger should be above 0 °C. Otherwise humidity in the outgoing air may condense, freeze and block the heat exchanger. A high enough incoming air temperature can also be achieved by Heat recovery ventilation, often with an earth-to-air heat exchanger, is essential to achieve German Passivhaus standards. Ventilation unit with heat pump & ground heat exchanger Ventilation unit with heat pump & ground heat exchanger - cooling Plate ground heat exchanger inside the foundation walls Main article: Ground-coupled heat exchanger This can be done by an earth warming pipe ("ground-coupled heat exchanger"), usually about 30 m to 40 m long and 20 cm in diameter, typically buried about 1.5 m below ground level. In Germany and Austria this is a common configuration for earth-to-air heat exchangers. In high humidity areas where internal condensation could lead to fungal/mould growth in the tube leading to contamination of the air, several measures exist to prevent this.

The pipes may be either corrugated/slotted to enhance heat transfer and provide condensate drainage or smooth/solid to prevent gas/liquid transfer. This is highly site dependent. One critical problem of using earth-to-air heat exchanger is being located in soils with underlying rock strata which emit radon. In these situations the tube needs to be airtight from the surrounding soils, or an air to water heat exchanger needs to be used. Formal research indicates that Earth-to-Air Heat Exchangers (EAHX) reduce building ventilation air pollution. Rabindra (2004)[] states, “The Earth-Air Tunnel is found not to support the growth of bacteria and fungi; rather it is found to reduce the quantity of bacteria and fungi thus making the air safer for humans to inhale. It is therefore clear that the use of earth-to-air heat exchangers not only helps save the energy but also helps reduce the air pollution by reducing bacteria and fungi.” Likewise, Flueckiger (1999) in a study of twelve Earth-to-Air Heat Exchangers varying in design, pipe material, size and age, stated, “This study was performed because of concerns of potential microbial growth in the buried pipes of 'ground-coupled' air systems.

The results however demonstrate, that no harmful growth occurs and that the airborne concentrations of viable spores and bacteria, with few exceptions, even decreases after passage through the pipe-system”, and further stated, “Based on these investigations the operation of ground-coupled earth-to-air heat exchangers is acceptable as long as regular controls are undertaken and if appropriate cleaning facilities are available”. An alternative to the earth-to-air heat exchanger is the earth-to-water heat exchanger. This is typically similar to a geothermal heat pump tubing embedded horizontally in the soil (or could be a vertical pipe/sonde) to a similar depth of the EAHX. It uses approximately double the length of pipe Ø 35 mm i.e. around 80 metres compared to an EAHX. A heat exchanger coil is placed before the air inlet of the HRV. Typically a brine liquid (heavily salted water) is used as the heat exchange fluid which is slightly more efficient and environmentally friendly than polypropylene heat transfer liquids.

In temperate climates in an energy efficient building, such as a passivhaus, this is more than sufficient for comfort cooling during summer without resorting to an airconditioning system. In more extreme hot climates a very small air-to-air micro-heat pump in reverse (an air conditioner) with the evaporator (giving heat) on the air inlet after the HRV heat exchanger and the condenser (taking heat) from the air outlet after the heat exchanger will suffice. At certain times of the year it is more thermally efficient to bypass the Heat recovery ventilation-HRV heat exchanger or the earth-to-air heat exchanger (EAHX). For example, during the winter, the earth at the depth of the earth-to-air heat exchanger is ordinarily much warmer than the air temperature. The air becomes warmed by the earth before reaching the air heat exchanger. In the summer, the opposite is true. The air becomes cooled in the earth to air exchanger. But after passing through the EAHX, the air is warmed by the heat recovery ventilator using the warmth of the outgoing air.

In this case, the HRV can have an internal bypass such that the inflowing air bypasses the heat exchanger maximising the cooling potential of the earth. In autumn and spring there may be no thermal benefit from the EAHX—it may heat/cool the air too much and it will be better to use external air directly. In this case it is helpful to have a bypass such that the EAHX is disconnected and air taken directly from outside. A differential temperature sensor with a motorized valve can control the bypass function. Seasonal thermal energy storage Air conditioning - Health implications Passive house - "Passivhaus" List of low-energy building techniques ^ Most HRVs are balanced ventilators in which heat is transferred from one airstream to another. These balanced HRVs are often called air-to-air heat exchangers (AAHXs). Central-exhaust heat-pump water heaters are HRVs but they are not AAHXs because they transfer heat from one airstream into water, not between two airstreams.

Another term often used is energy recovery ventilator (ERV). All HRVs transfer sensible heat from one airstream to another or to water. If latent heat is also transferred, then an HRV can be called an ERV. While there are specific differences between these different terms, many people use HRV, AAHX, and ERV interchangeably. The Healthy House Institute. Understanding Ventilation: How to Design, Select, and Install Residential Ventilation Systems. ^ D. Denkenberger, M. Parisi, J.M. Pearce. Towards Low-Cost Microchannel Heat Exchangers: Vehicle Heat Recovery Ventilator Prototype. Proceedings of the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT), 14–16 July 2014, Orlando, FL, USA. 1. Rabindra Nath B, Shailendra Kumar M, and Pawan Basnyat; Use of Earth Air Tunnel HVAC system in minimizing indoor air pollution; Air Quality Monitoring and Management, proceedings of Better Air Quality 2004. 2. Flueckiger B, Monn C; Microbial investigations and allergen measurements in ground-coupled earth-to-air heat exchangers;