Implementation of Green Energy for HVAC of Multi-Use Public Facility

1. Implementation of Green Energy for HVAC of Multi-Use Public Facility • Josh Bouchie • Dylan Kugler • Tim MacIsaac • Duncan MacRae

2. Florida • Upon closer examination of the contest rules it was discovered that Canadian students are also expected to construct an HVAC design for the Ginsburg Tower located in Orlando, Florida. • At this stage in our design the change in location did not affect our design to a great extent as we had only completed fresh air (ventilation) requirements which will not change based on location. • The change in location will ultimately lower the need for heating, as well as increase the need of mechanical cooling.

3. Geothermal Design • Several factors were considered when the decision was made to abandon a design incorporating a ground source geothermal system • These concerns were discussed with Ron KellP.Eng of A.H. Roy and Associates to see if our concerns were validated. The results of these discussions are as follows.

4. Thermal Diffusivity Thermal diffusivity is a ratio of the soils thermal conductivity and the product of the soils density and specific heat (the capacity of heat transfer per kilogram of soil) Originally when we had selected Ottawa, a thermal diffusivity was found to be approximately 4. Florida, and specifically Orlando has a thermal diffusivity of nearly double that at 7. Soil with a high thermal diffusivity is excellent when heating but is not well suited to cooling as it expands the number of vertical borehole wells. Such a large building with a design cooling load of nearly 600 tons, and an approximate estimation of a single 500 foot well per ton of refrigeration means that 600 or more wells would be required which is far too large.

5. Water Source Geothermal • Lakes, Oceans, Rivers or wells can be a source of geothermal energy. • For one ton of cooling it is estimated that 3 gallons per minute of fluid flow are required to attain the proper amount of heat transfer. Our design would require 1800 gallons per minute of water flow, this level of flow in not only unattainable but environmental regulations do not typically allow such a large amount of water to be removed from a source A municipal source could be used but such a high cost per gallon of water would make the system unattractive financially.

6. ASHRAE Recommendations • In Hospital settings, ASHRAE recommends an indirect cooling application to avoid large swings in cooling. • Indirect implies the production of chilled water to coils which will have air blown over it to achieve cooling. • Geothermal design requires the removal and transfer of heat directly from the room to the refrigerant coil. • Indirect cooling methods also keep noise levels to a minimum as there is no compressor in the ceiling which will be audible when operating

7. Central Cooling Plants • Central chillers operate on the vapor compression cycle and provide chilled water at 45 ˚F which is then pumped to each air handler. Air is blown over top of the coils to cool the air down to 55 ˚F . • The air is then distributed to the zone terminal corresponding to the block of rooms it serves where it will be reheated to room temperature at 70 ˚F • This excessive cooling and reheat seems wasteful but will be discussed later in the presentation.

8. Central Cooling Plants • Benefits of a central cooling plant: • Noise-limited to mechanical room • If something is to go wrong with the system, the problem is isolated to the mechanical room and can be quickly addressed as opposed to having to locate and individual heat pump that has malfunctioned somewhere in the building.

9. Determining Cooling Requirements Done with trace 700 software. Cooling Calculations take into consideration the following: Building Envelope – The existing conditions of the building if it were unoccupied. In this case it means the effect of the outside conditions including solar load, infiltration, wall, roof, and floor loads. Equipment Load - Lights, hospital equipment, and computers all give off heat and must be accounted for when cooling a space. People Load – The amount of people in a building has a dramatic effect on the amount of cooling required. Things such as respiration and body heat add to the total heat of a space.

10. Sample Patient Room Cooling Calculation Each Calculation is done on what is referred to as a Design Day, which is the worst possible case. These building loads are in addition to the load created by having physically cool the supply air down to the correct temperature

11. Pyschrometrics Definition: Is the study of...... Sensible and Latent Heats Humidity : ASHRAE permits a relative humidity range of 30-50% in health care facilities. Application of the First law of thermodynamics • What is Humidity? • Air has a certain moisture content in it. The level of moisture in air is different depending on Temperature and Pressure. Relative Humidity is the ratio of water in the air compared to the maximum possible under the current temperature and pressure conditions

12. Simple Heating or Cooling Simple heating or cooling of air does not change the water content of the air, it merely changes the temperature of the air. This is done as a fine tuning measure just before the air is distributed to the space. In our case this will be done by reheat coils located in the ceiling outside of our rooms.

13. Dehumidification The most common form of dehumidification is cooling the air at a constant pressure. Given the Temperature and relative humidity of incoming air (calculated with a spin physcrometer) you can calculate the air Dew Point Temperature. When the air is cooled at a constant temperature past the dew point temperature water will begin to condense out of the air. This phenomenon is often seen in the morning in the summertime During cooling design we will need to do large dehumidification in our air handlers

14. Humidification In winter months the outside air is dry and cold. The relative humidity is less than the ASHRAE recommendations so water must be added. This can be done in two ways: Water injection – Air is blown over water Steam injection – Steam is injected, increasing the temperature and relative humidity of the air. We will provide steam injection humidity at our air handlers.

15. Adiabatic Mixing Occurs when two moist streams of air are mixed together. This will occur at our air handlers where the return air from the space is mixed with the incoming air. Adiabatic mixing produces supply air that is a waited average of the incoming fresh air and return air. It is called adiabatic because it requires no work input or heat transfer.

16. ASHRAE Chart Now that we know the 4 processes that are used in HVAC applications we will show how pyschrometrics were applied to our Heating and Cooling Designs.

17. Cooling design choice • Constant Air Volume with Terminal Reheat • Produces chilled water on one side and heated water on the other. • Requires a cooling tower to reject heat to the atmosphere

18. Design Disadvantages Cooling towers simply throw heat to the atmosphere. Large amounts of useful heat are thrown away Terminal reheat requires heated water at the distribution terminals which means more energy input.

19. Advantages As opposed to variable air volume where the temperature of a room is controlled by manipulating the volume of air being delivered to a space, a constant air volume system maintains pressurization in the room which is crucial in health care facilities.

20. Cooling Towers

21. Green Solution We researched into different models of chillers and found a unit by McQuay called a Templifier Unit. These units operate the same way a traditional chiller does with the exception that the warm water produced is ran through an additional heat exchanger that is connected to a building loop that will supply our reheat terminals with 140 F water necessary to bring the air from 55 to 70 F. These units are shown to reduce energy consumption by 30-50% due to the fact it captures a significant amount of heat prior running the water through the cooling tower.

22. Calculating Heating Demand Small radiant panel heaters will be placed on exterior walls to account for heat losses on colder days

23. Heating System Heating design day is low compared to Canada, our simulation shows that heating is rarely needed. All hospitals have large steam plants used for things such as dishwashing, laundry, and equipment sterilization. We will use a steam to water heat exchanger located in the mechanical room to provide heated water to supply our radiant ceiling panels in rooms with exterior exposures

25. Questions????