Description of selected projects from 50 years of innovative HVAC design presentation.
Shlomo RosenfeldDescription of selected projects from 50 years of innovative HVAC design presentation.
Dec. 30, 2016 Draft by Shlomo Rosenfeld, PE.
The intent of my talk is to describe several innovative energy conservation HVAC projects in order to inspire students and faculty. Some of the objectives of the HVAC system are to provide a comfortable environment, better IAQ, improve productivity and be energy efficient with reasonable cost for the energy conservation. Years ago, I coined the phrase "The-Use-Of-The-Available" for a design process and I will highlight this in my description of the design of HVAC systems of several projects. A judge in an Energy Competition described it as "Here is a very careful pairing of a simple energy-conserving design with sophisticated controls of conventional mechanical equipment."
Conventional cooling by chillers, pumps and cooling towers during the day had a coefficient of performance (COP) of 3.9. The cooling towers and pumps cooling water at night had an incredible COP of 22.
Energy from a data center air conditioning heat rejection was ‘available’ to be recover as hot condenser water at 90 F, stored in two tanks, and useed to heat the building. 90 F hot water is relatively low temperature for heating hot water which is normally at 180 F. The cooling coils in the air handling units are idle in the winter they have large number of rows of tubes and large fins area. So, the cooling coils were ‘available’ and harnessed to perform heating during the winter and capable of using the 90 F hot water eliminating the need for separate heating coils, associated cost and energy use.
Further analysis of what is ‘available’ in the unique Reno weather shows also hot summer temperature and very cold winter temperature with many hours of mild temperature between. HVAC transmission load is the only space HVAC load which changes phase; heat gain in the summer and heat loss in the winter. All the rest of the space HVAC loads are cooling loads. The air distribution system consisted of a cooling only interior variable air volume (VAV) system, and a perimeter constant air volume variable temperature system. The perimeter system was sized to handle only the building skin transmission heat losses or gains. There are many hours during which the weather is mild in Reno, i.e., negligible transmission gain or loss. Thus, the perimeter air system is turned off when the outside air is between 60 and 85F, resulting in simple fan power energy conservation. In addition, during the winter the perimeter system uses 100% return air from the interior recovering the ‘available’ energy, from lights, office equipment and occupants, and transferring this interior energy, which is normally wasted, for heating perimeter zones and saving energy.
Analysis of what is ‘available’ in the unique San Jose weather resulted in the concept of using 100% outside air with a modified ‘available’ technology of the "run-around" heat recovery (RAHR) system which, in this case, has advantages over the conventional return air concept. When using 100% outside air and 100% exhaust air, it allows to recover energy from all the ‘available’ ‘used’ air; return air and exhaust air. In addition, the annual efficiency of the RAHR could be designed to approximately 70% since reduction in air volume (VAV) improves the efficiency of the RAHR system. The use of 100% outside air improves the IAQ, allows code compliance of minimum outside air at the minimum air volume of a VAV operation resulting in the first VAV system approval for hospital in California.
Moreover, 100% outside air and 100% exhaust air requires only two duct systems; supply and exhaust. Comparing initial cost of three ducts system vs two duct system shows that the saving compensates for the cost of the RAHR system and additional saving is left. The result is energy saving and initial cost saving; the best of both worlds.
Hospitals include kitchen with large refrigeration systems requiring to reject the refrigeration condenser heat. Now the RAHR system is ‘available’ to reject that heat allowing to recover this heat in the winter and discharge it to the exhaust air in the summer. By elimination of the kitchen refrigerators heat rejection equipment, again we accomplished energy saving and initial cost saving; the best of both worlds.
- Analysis of what is ‘available’ in the unique
The cooling capability of evaporative cooling equipment depends primarily on the ambient air wet-bulb (WB) temperature. In evaporative cooling process, the temperature of the cooled water leaving the evaporative cooling process is limited by the ambient air WB temperature. This limit challenged HVAC engineers for years. This part describes how the ambient WB temperature limit was conquered and how water can be cooled by evaporative cooling below the ambient WB.
- 100% outside air system with multi-level heat recovery HVAC system more efficient than a conventional return air system while improving the IAQ, supporting the well-being of staff and patients Remember the
The system design includes the following:
- Reclaim condensate water during
- Heat recovery from reclaimed cool condensate water to pre cool air of selected air handling units
The challenge was that no building simulation program could simulate an HVAC system with all of the above components which many of them have never been done before. I worked with the scientists at LBL who developed and maintained the EnergyPlus program and they could not simulate them. So, I developed a simulation program, of my own, for hospital HVAC systems to compare options in order to select the most effective and efficient options.
This project won First Place at the Building Healthcare Awards 2015 in the following categories: Best Hospital Design, Best Sustainable Hospital Project and People's Choice