Using the AEDG in large hospitals
Case study: Saving energy at a Denver hospital
As an example of the impact of achieving the target energy savings, information and projections for a new, large, energy-efficient hospital in the Denver area are shown. Actual energy usage has been tabulated and graphed, with the AEDG 50% energy use target entered to calculate projected annual energy cost savings. This facility currently is consuming 210,000 Btu of energy per year, well below what we typically find for new hospitals. Annual utility cost is slightly more than $1.6 million. If the AEDG 50% reduction goal of 107,000 Btu/sq ft for climatic zone 5B is obtained, with the same proportion of electrical and gas use, savings would be more than $800,000 per year.
In this example, 61% of energy used by Btu is fossil fuel energy, and 39% is electrical energy; it is not likely that electrical energy use can be cut in half. This implies that to obtain the goal, the greater portion of reduction will have to come from fossil fuel use for heating and humidification (see Figure 4). Proportionately, electrical savings would be less, and fossil fuel more, with annual cost savings closer to $450,000 than $800,000. In any case, it will take more than adjusting lighting and HVAC settings to obtain the energy use reduction goal. Plug loads from items like medical equipment will have to be addressed.
In conclusion, energy efficiency must be long lasting and sustainable. If planning is followed by simplicity of design, quality construction, validation, loop tuning, and operator education, it will be real and sustainable. It will last longer, and not only be energy efficient initially but also remain energy efficient as modifications to improve or expand are implemented.
Lastly, we stress the importance of tracking and documenting energy usage. Once a full season of performance has been completed, final proof will be actual energy usage. It may not meet or beat the 50% AEDG energy target for performance, but we will be able to confirm the actual Btu/sq ft. Hopefully, we will have reached the goal, but if not, the intent of energy efficiency will have been at least partially fulfilled—there will simply be more work to be done, with real loads, real equipment, and real weather.
Pete Sabeff is president of Engineering Economics Inc., where he has been troubleshooting and commissioning hospital HVAC systems for most of his 40 years in the business. He began as a controls applications specialist, became an energy consultant, and for the past 28 years has been an owner’s representative and commissioning agent.