HEATING AND AIR CONDITIONING
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HEATING AND AIR CONDITIONING |
Wall heating systems
Floor heating systems
Floor heating systems
Forced air ducts
Examples of fuel
Wood burning heating system
Central gas heating system
Geothermal energy
Traditional heater (left) and condensation heater (right) heat loss chart
Water cooler with water coolant
Large capacity water cooler with centrifugal compressor
Directly powered refrigerating system
Hot water absorption powered refrigerating system
Solar panels
Hot water absorption powered refrigerating system
Windmills
Co-generation system
Co-generation equipment |
The heating and air conditioning system must be able to meet the following requirements: - distribution and architectural compatibility, maintaining the flexibility of the rooms considering their convertibility and various uses, - guarantee to maintain a comfortable temperature depending on the number of people, the type of activity and the season, - economy and ecology of the heating/AC system. These needs translate into a few requirements independent from the techniques and methods adopted in different countries; therefore, they are universally valid: - every room must have independent thermal-hygrometrical adaptations and ventilation in order to maintain constant temperature avoiding unexpected changes caused by crowds, irregular solar exposure and sudden weather changes, - possibility to modify the heating/AC distribution system, depending on the space configuration and it must be easily replaced and integrated, - every room must be independently controlled, therefore, regulate fundamental environmental parameters, for example: * temperature * humidity * air quality (CO2%)
These settings will allow the interface with entire system's central controls, therefore, only the necessary portions of the system will be activated through consent coming from the activated control system. From these requirements, we pass to another; the system must be able to quickly change from heating to cooling.
SYSTEM SOLUTION PROPOSAL Since the various areas in the building must be activated only if necessary, when personnel is present for activities, the building must be kept at a minimum temperature so the furniture, material, paint, etc. do not deteriorate. This temperature, approx. 15-17°, could be maintained thanks to floor panels or wall panels if there is a raised floor. This type of system guarantees total flexibility of the internal walls. It is appealing esthetically and has big advantages in terms of energy consumption; this is because the temperature of the water that must circulate within the panels is from 25 to 30°.
The various building modules will be served by a single unit able to: - distribute forced air heat, - distribute forced air conditioning, - ventilate with clean air based on the amount of CO2 in the environment. The single units, cold liquid, hot liquid and air, will be fed by ducts in the corridors or a symmetrical layout in large halls. This will guarantee a notable flexibility in the system. In the case that more than one unit serves one area, the sensors can be united electrically or with regulation software. The extraction of bad air will be performed by intake ducts that will recycle the air. The extractors could be connected to a remote area near the heating/AC room. The three principle systems, heating, AC and air treatment, could be placed were they are most easily supplied with energy.
Useable energy sources The energy source choice to power the school building must keep in mind the following points: - energy available, - economic resources available, - depreciation time for particularly costly technological solutions that have managing benefits and respect the environment, - environmental impact, with particular reference to adaptation to renewable energy sources and in compliance with the Kyoto Accords, - overall energy balance of the adopted solutions.
Available energy sources should be analyzed one by one. Remember, usually a mix of sources must be used to cover the yearly needs. - Solid, - Wood, - Expressly produced material, - Recyclable material destine for the landfill.
Wood could be considered as an energy source when the wood is not trees cut specifically for fuel. It is also possible to use scrap from furniture factories or other sub-products with wood base that would otherwise end up in the landfill. The existing technology yields 90-92% combustion and a more acceptable environmental impact compared to ordinary systems; the emissions are practically nothing in advanced systems. These systems can range in yield from 20Kw to tens of Mw and can produce hot water, steam and therefore, generate electricity with a turbine.
Natural combustible liquids are becoming more popular due to the low price compared to fossil fuels. Since the type of use is similar to those of hydrocarbons, the systems that exist require limited operations to make them function. With natural combustibles, the increase of CO2 in the atmosphere, only that of cultivation, in compliance with the Kyoto Accords. The critical point could be the presence of chemical solvents in the combustible to make sure the fats remain solvent. - Natural Gas - Methane - Exhaust condensation techniques
Methane is an ecological fossil fuel. In fact, its use is encouraged and promoted on a large scale. This combustible can be used in combustion techniques that allows high yield, 107/108% of the P.C.I., by recovering latent heat in the steam in the heater's exhaust. Moreover, the condensation contributes to destroy nitrous oxide (NOx) that represents the largest polluting element in methane. Generally, condensation heaters produce less nitrous oxide than ordinary generators; therefore, this type of generator could produce less than half the NOx a traditional heater would produce. Finally, to accentuate the effects of condensation, the emission temperatures, and therefore the return temperatures, must be as low as possible. For this reason they are ideal for floor and wall panel systems as an integrated support to solar panels. - Renewable - Geothermal - Heated air pumps - Heated water pumps
Heat pumps are thermodynamic machines that recover heat from low temperature fluid, source, and give it to another fluid with a higher temperature. This process consumes less energy than what it recovers. The energy balance must also be compared to the economic balance, since the most important factor is the cost of energy. The energy consumed could be: - electricity; machines are normally refrigeration systems to cool industrial facilities, - fossil fuels; heaters that burn methane and make a refrigeration system possible, - thermal; heaters that do not use combustion but use hot fluid to make a refrigeration system possible.
Remember that heat pumps generally produce hot water at approximately 45°C. In particular cases the temperature could get to 60° if a low temperature source is used. This system is adapted where heating systems are already in use with low temperature fluid vectors Other uses of heat pumps are based on the type of fluid use as a source, which could be: air coming from: - outside - thermal exhaust - cooling particular areas; data processing centers, technology centers water coming from: - surface water, streams, rivers, lakes, seas, and sewers - underground water drawn from a well Obviously, the higher the temperature source fluid you have with constant characteristics, the higher the yield.
Hot water production with solar panels Solar panels allow water to be heated thanks to the greenhouse effect created inside them. This effect can be accentuated with a few tricks in order to increase their efficiency. The quantity of hot water produced is inversely proportional to its temperature. Solar panels can be used for the following: - produce hot water for showers and baths; this is the most commonly known use, - produce hot water for low temperature heating systems, in particular, floor and wall panels, - produce hot water for summer cooling using hot water powered absorbers,
Combining the possible uses above, it is possible to use the panels during the entire year meaning the costs will be amortized more quickly. The problem of energy integration during the night or on cloudy days remains. A reserve tank, necessary to satisfy peak demand periods, would not be sufficient, so another energy source is necessary.
Hot air production with solar panels While maintaining a comfortable temperature in a building, it is essential to guarantee good air quality. Often, the mass of air to treat is notable so energy costs are substantial. Generally, a mass of air equal to a few times the building's volume must be heated to approximately 20°. Heating the reintegrated air can be done with sheet metal or aluminum walls with tiny holes forming a cavity between it and the external wall. The sun heats the surfaces creating convection that is aspirated by the tiny holes and conveyed upwards into ducts and introduced, already warm, into the air treatment equipment to complete the treatment, filtering, regulating temperature, pressurization, etc. Remember that the energy spent to heat the air again could be equal to two to two and a half times the cost to heat the rooms.
Heating with photovoltaic panels Photovoltaic panels are made of cells built with a sheet of silicon that if exposed to sunrays produces electric energy. On the average, one meter of photovoltaic panel produces approximately 80 to 90 W of electricity. There are two types of systems: - connected to the main power In case there is no sun, nighttime or cloudy days, the electric power takes over to satisfy the energy requirements; - independent of the main power When there is a lot of sun, the surplus energy is saved in accumulators that takes over when there is not enough power.
Windmills If the annual average of wind reaches a preset amount, it is worthwhile to install a windmill with an electric generator mounted on a 20 to 30 meter tall pole. These devices have a few disadvantages the must be noted: - they are not pleasant to the see, - they are sometimes noisy and can not be placed near a building.
Co-generation Co-generation allows electricity and heat to be produced contemporarily with endothermic motors in the form of hot water. The energy yield of these devices is very high, approximately 84-86%. Particular attention must be paid to the choice and size of the co-generating equipment because all the energy produced, electricity and thermal, must be used contemporarily to make the cost of the devices worthwhile. |
