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McSweeney
Engineering
Engineering
Sustainable design is the use of environmentally friendly cleaning products, water conservation and energy conservation as well as ensuring that the indoors have the highest quality environment possible.
Having a high quality indoor environment includes having the ability to see outside and use the daylight as opposed to using electric lights. A high quality indoor environment also ensures there is enough fresh air to prevent odors and disease causing particulates or gases, such as bacteria and mold, from accumulating indoors. The final aspect of a high quality indoor environment is to ensure that it is comfortable for the occupants, in their typical attire for the time of year.
Some sustainable concepts that we have evaluated:
Air Conditioning: There are many "commissioning" tasks that should first be reviewed to see if energy savings can be accomplished. First of all the system needs to be reviewed to ensure that it is not creating a "perfect" environment when the building is unoccupied. Additionally the temperatures that the spaces are being kept should be reviewed.
Dirty filters should have alarms so that they are regularly changed and do not cause the fan to unnecessarily consume more energy than should be required.
If the system serves multiple spaces the addition of Variable Air Volume (VAV) devices and Variable Speed Drives on the fans should be investigated since these technologies can lead to substantial savings by controlling the conditioned space to meet the load and therefore prevent overcooling.
One area that we have recently been involved is the use of INDIRECT and DIRECT Evaporative cooling systems to meet the cooling needs in Data Centers. We developed the concept for an Indirect/Direct cooling scheme for a data center in Washington State as well a 2nd System for a client in Oregon Both of these concepts utilized a Spec-Air Air Handler.
Additionally we have developed a concept for the use of a recirculation system that provides cooling using an indirect Evaporative cooling scheme with a DX assist for hot days that can be used in NJ. This recirculation Evaporative Cooling System can be used with only the Evaporative Cooling Scheme for over 6000 hours per year and can result in a data center PUE of less than 1.3 and maybe as low as 1.25.
Heating: based upon some recent information that we modeled, McSweeney Engineering recommends not heating using a ducted air system. Placing heating coils in VAV boxes or in typical reheat locations increases fan energy and boiler energy due to the greater need for heat in an air heating system. As we all know, heat rises naturally and trying to force heat down does not work very well. The best way to heat is with radiant, because of the lower temperature water required. Alternatively baseboard or radiator heat will do a fine job by developing natural air currents. The heat source, boiler, should always use a fully modulating gas valve and a temperature reset schedule, either load based or outside air based, to save energy at the boiler.
Radiant Heat: Radiant heat systems, whether they are below floor staple-up, embedded in the sub floor or embedded in concrete provide a nice level of comfort and are very energy conscious. These systems save energy because they typically operate with circulating water temperatures below 120 degrees Fahrenheit. A typical radiator or baseboard system requires hot water temperatures of either 180 or 200 degrees Fahrenheit. The difference in water temperature has a dramatic affect on how much fuel the boiler consumes. Lower temperatures lead to less fuel being burned.
Controls: Using state of the art controls on both the ventilation and the heating system can make a big savings difference. Having a boiler with fully modulating control valve will allow the boiler to cycle less often. Cycling causes many losses as the boilers have a purge cycle when they shutdown that clears exhaust fumes but also cools the boiler. Cycling the burner less often saves energy.
With the air conditioning system an economizer that uses partial or all outside air for cooling, based on the temperature and humidity of the outside air, can again dramatically reduce cooling loads. This economizer operation can be done residentially with motor operators on operable windows.
Green Cleaning: There are many cleaners that have been approved as environmentally sensitive and that work just as well as the non-friendly cleaners. A list of these "green" cleaners can be found at the Green Seal Website. http://www.greenseal.org/findaproduct/index.cfm
Solar Hot Water: Solar hot water can be used to make domestic hot water, in place of the hot water heater, or space heating water. The different hot water temperatures dictate different types of solar panels and therefore different costs. From what we have seen, solar domestic hot water typically provides a payback in the 3 to 6 year timeframe for a small commercial facility and for a family of 4 a system can be installed for between $8000 and $10,000 in 2009. With a savings of $2,000 to $3,000 per year, this usually works out pretty good.
Solar space heating on the other hand tends to be more expensive and the paybacks tend to be a bit longer, 9 years to 12 years. This system also needs a way to reject the heat created during the summer since the system cannot be turned off, heating a swimming pool is very effective. An alternate summer heat rejection system may be an outdoor air coil, such as the air conditioning unit that is outside, to reject the heat to the outside air.
With both the domestic hot water heating and the space heating a gas fired, or in the worst case electric water heater, is required as a back-up and for the times when the system cannot keep up with demand.
Solar Power: We have reviewed utilizing solar panels to create electricity for both commercial and residential applications. Even with the 30% federal incentive, we have found that solar electricity takes between 9 and 11 years to payback. This is the the choice that needs to be made, is 9-11 years too long? As always each individual system should be evaluated, since there are many variables that go into the cost of these systems.
The solar PV, photovoltaic, companies do not tell the same story, they usually indicated less than a 5 year payback. As always with corporations that are selling a product they look at the best case to make there products look better. One of the biggest misnomers is the use of SRECs, Solar Renewable Energy Credits, to off set some of the cost. SRECs in 2008 were worth about $475 per Megawatt of power generated. The solar companies use this value and sometimes more for the life of the panels, about 25 years. This may or may not be the case since no one can predict the future.
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