SUSTAINABILITY


Similarly, electrical systems are sized


to accommodate the full load of each piece of equipment, resulting in electrical systems with high degrees of oversizing, especially as the loads aggregate. The lack of accurate consumption data exacerbates the growing impact of the consumption of the equipment itself, snowballing the problem into a huge opportunity for improvement.


Assessment and validation Over the years, many champions have tried to chip away at this growing sustainability challenge. For example, 20 years ago, the US Green Building Council created the Leadership in Energy and Environmental Design Green Building Rating System (LEED). The new green building assessment and validation tool created a revolution in the way that building developers, designers, constructors and operators thought about their buildings. Development teams everywhere started to pay attention to the carefully scripted points to prove that their buildings were ‘green’. Unfortunately, early versions of LEED did not work well for most acute care healthcare buildings for a number of reasons. As a result, the American Society of Healthcare Engineers and Healthcare Without Harm collaborated with a group of volunteers to create a parallel, voluntary, self certifying set of criteria called the Green Guide for Healthcare (GGHC).2


Among the challenges posed by


healthcare was the relatively large and growing level of energy consumption driven by the profusion of medical equipment. To address this challenge, the GGHC borrowed from another newly created industry specific sustainability design guide; this one focused on laboratories – Labs 21.3


Labs 21 was the


first green building rating system that recognised the impact of equipment inside the building on overall building energy consumption. GGHC borrowed this concept and applied it for the first time to the growing importance of medical equipment as part of the enterprise energy consumption of a healthcare building. It also sought to encourage the consideration of low energy medical equipment as part of the selection process. Subsequent to the GGHC, others


started to pay attention to this growing opportunity.4


The United States


Environmental Protection Agency explored, but abandoned the effort to create an energy star programme for medical equipment.5 project6


developed a range of whole


building strategies for hospitals, aimed at those that would consume no more than 100 kBtu (1000 British thermal units) per square foot per year. In all of them, the energy consumption due to medical


66 0


Climate zone 1A – representative city: Miami, Florida Baseline model


Low energy model


With all energy reductions accounted for, the percentage of total load represented by medical equipment is one of the most significant drivers of consumption.


IFHE DIGEST 2018 100 50 The Targeting 100 Cooling systems for medical equipment


The design of cooling systems for medical equipment is critical to their reliable operation. More often than not, equipment manufacturers overstate the power and hence cooling requirements of their devices. This is most obvious because most equipment is listed in increments of kW and rarely is this actually the case. The under reporting of cooling requirements is rare and the results are pretty obvious in that it is not possible to maintain the space temperature. Often a cooling engineer will have to design for multiple manufacturers and the cooling load can easily vary by a factor of two for a given type of imaging equipment. However, the overstating of cooling requirements can have significant energy consequences. Most hospital cooling systems are constant volume, which means that the amount of air supplied to a space does not vary and the way to control the room temperature is by varying the supply air temperature. If the cooling load is less than what was designed for, then the heating coil is activated. Reheat in hospitals makes up about 30 per cent of the energy consumed, so even though the amount of reheat that has to occur in one room might not appear to be large, it adds up to a lot in the whole building. To help one particular hospital reduce its energy spend, the authors looked at its catheterisation laboratories. The air flow to the equipment closets matched the cooling load provided by the imaging manufacturer. They knew it was oversupplying the equipment rooms because the AHU supply air temperature was 55˚F but the supply to the room was 68˚F for a room temperature of 70˚F. So, of the 15 degrees of cooling offset, two degrees was used for cooling and the remainder was reheated; that is an 85 per cent waste of cooling energy. The fix involved fitting remotely controllable air valves on the supply and exhaust that could be adjusted through the building management system to reduce the air flows. The ideal set up is to use a variable air volume (VAV) arrangement that allows only the right amount of air to be supplied to maintain the room temperature.


equipment stayed constant and therefore constituted an increasing proportion of the overall energy consumption of the building. The ‘plug load’ problem persisted through the development of the US Department of Energy advanced energy guides for healthcare, which relegated this issue to an “additional implementation idea”.7


Further research In the face of this seemingly intractable need, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) undertook a research project to measure the true energy consumption of medical


300 Source: ASHRAE, Advanced Energy Design Guide for Healthcare 250


n Refrig (electric) n Humid (electric) n SWH (gas) n Pumps (electric) n Fans (electric) n Cooling (electric)


200


n Reheat (gas) n Preheat (gas) n Ext light (electric) n Int light (electric) n Ext equip (electric) n Int equip (gas) n Int equip (electric)


150 equipment.8 In the end, the project


determined that the best thing was to create a protocol for how to measure the energy consumption of the equipment. The gist of it is that there is no good data out there and that you can’t rely on the manufacturer’s nameplate data. The paper breaks this down into four imaging modalities: X-ray, ultrasound, magnetic and nuclear. The recommended test is to obtain amperage readings for the circuits feeding the various system components. The protocol breaks the test data down into three modes: sleep, idle and high use. The test data shows very little difference in the three modes and could be useful in helping to change the industry as this is


Annual energy end use intensity (kBtu/ft2


yr


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