Saving money in hospital electrical distribution systems
There are two ways to attack the rising electrical costs of operating a hospital: UPS upgrades and co-generation.
There is plenty of uncertainty surrounding hospitals: reimbursement rates, census, power failure, and hurricanes. However, one thing is certain: utility costs for these facilities will continue to rise.
Designing a hospital electrical system is challenging. Primarily, it has been focused on providing a maintainable and reliable electrical system. Many hospitals have joined the greening of our industry by pursuing LEED or setting energy goals with other prescriptive documentation programs. This has typically been part of their altruistic core philosophy as good stewards of the planet. I’ve been lucky enough to work with several hospital networks that have this belief. Their hard work on the cutting edge of design has enabled the development of many green technologies that we commonly use today (see Figure 1).
However, let’s ignore the thrum of the green drum in the background for a moment. Every hospital employee I’ve worked with—whether it’s the facility director, electrician, or CFO—is very interested in saving another type of green: money. Infrastructure and utility costs are expenses that hospital management must control to accomplish the mission of saving lives.
A typical hospital consumes an inordinate amount energy compared to a conventional building. According to ASHRAE Advanced Energy Design Guides, hospitals account for less than 2% of the floor space and almost 6% of the energy consumed in the U.S. The average large hospital consumes 234 kBtus/sq ft according to the U.S. Energy Information Association.
So what does that mean to an electrical engineer? It means that whatever energy saving measures we implement could be two to three times as effective as they would be in a conventional building—just due to the size of the loads. Unfortunately, the largest portion of the energy used in a hospital (54% according to ASHRAE’s Advanced Energy Design Guide for large hospitals) is for HVAC and domestic water heating, which are outside of the electrical engineers’ direct influence.
Lighting is traditionally seen as the big energy saver target for electrical engineers. According to the U.S. Energy Information Administration, lighting is responsible for 21% of the total energy used in commercial buildings. In hospitals, the usage can be 8% to10%. Energy lighting design has been covered by many authors. However, it isn’t the only opportunity—especially in a hospital.
That leaves more than 35% of the hospital’s loads in the category of other. In commercial buildings, there is a movement to control many convenience power loads with building automation. Since this is not a viable option in many of the patient care areas of a hospital environment, we need to be a little more creative.
Saving energy, maintenance costs
Upgrading a hospital’s UPS system with a modern centralized UPS is one way to save money and energy. Hospitals constantly upgrade technologies and house cutting-edge technologies that require premium UPSs and/or power conditioners. Unfortunately, many hospitals are plagued with a hodge-podge of UPSs of varying sizes and efficiencies. Typically, they are deployed in a point-of-use manner for individual loads during each expansion, project, or initiative within the constantly evolving building infrastructure. This distributed approach leads to many oversized UPSs that function in the lower range of their efficiency curves. Typically, these UPSs are from various manufacturers with inconsistent features and labeling. In general, they are maintenance headaches and big energy consumers.
The majority of UPSs in a hospital typically fall into two categories: IT department and diagnostic imaging department (i.e., radiology, scanning, x-ray). The load profiles and uses for these two categories are significantly different and should be always considered apart from each other. That doesn’t mean that they cannot be on the same UPS, but close attention must be given to how the systems are joined.
The IT department’s UPSs are typically located in either the IT closets or the data center. Many IT distribution closets contain low-cost cord-connected standby UPS units. They are surprisingly efficient because they are one step removed from a battery charger. Occasionally, a client will have a cord-connected line interactive UPS in a closet, which is also relatively high on the efficiency scale. Replacing these units with power from a central UPS will not offer significant energy savings. However, doing so would strictly be based on the preventive maintenance advantages.
The IT department’s data center is usually a better opportunity to save energy. In my experience, this could be just about anything depending on how the facility has existed. I’ve seen vintage 3-phase double conversion units as well as single-cord-connected UPSs strewn across the floor. There is often an opportunity to combine multiple disparate units of lower efficiencies into a single UPS system. To clarify, I generally consider a modular UPS system with individual maintenance bypass vs. a single UPS unit that would qualify as a single point of failure for the department. This point of failure is a much larger discussion, but typical hospital clients are satisfied with dual UPS technologies that they can maintain.
Most IT department loads don’t vary significantly with the time of day. Therefore, there are limited opportunities to schedule the level of power protection provided in these areas.
Conversely, the diagnostic imaging department probably presents the biggest opportunity for energy savings in a hospital. Each piece of medical equipment in this department tends to have a UPS that was furnished as part of the equipment package from the medical equipment manufacturer. The UPS is normally stuffed into a room in the actual diagnostic imaging department. Because the installation of the medical equipment was the priority when the unit was installed, electrical characteristics are rarely considered. Typically, these UPSs:
- Have lower efficiencies
- Don’t have modern capabilities for energy-saving modes
- Aren’t capable of scheduling between full online conversion and energy-saving mode
- Are grossly oversized for the given load type
- Don’t communicate with the building automation system.
Developing a single UPS system for the entire department is relatively easy, depending on the quantity and types of imaging equipment within the suite.
For illustrative purposes, consider a hypothetical imaging and surgery department with two MRIs, two CT scanning units, an IMRI room, and an ICT room with the equipment manufacturers providing a UPS for each piece of equipment. Assessing the continuous demand and the inrush currents for each piece of equipment allows the development of a central UPS solution that will save capacity (see Figure 2).
In this hypothetical solution, the single UPS would save 600 kVA of unnecessary UPS capacity. Traditionally, extra capacity is a good thing in electrical design because you don’t pay much energy consumption for the additional capacity, but in this case the extra capacity becomes very expensive.
The first money saver would be saving battery capacity and the ongoing maintenance of these batteries. Saving 600 kVA of battery capacity saves the owner nearly $100,000 of material cost every 4 to 6 years for 10-year VRLA batteries. This doesn’t include the cost of the labor to install the replacement batteries or any associated disposal costs. Even if the client uses in-house staff, this is conservatively a $20,000/year savings.
The second money saver is the opportunity to use more energy-efficient modes during after-hour periods. The proposed single UPS would be specified with the capability to provide 96% or 99% efficiency mode during off hours (most hospitals don’t run their imaging department equipment at night). Using a 99% efficiency mode 10 hours a night with the aforementioned hypothetical case (approx 500 kVA) saves the owner more than $30,000.00 annually—including HVAC costs.
Cost of real estate: The average 150-200 kVA UPS uses 80-100 sq ft of premium floor space within the diagnostic department—space that most departments cannot afford to sacrifice to non-revenue-generating uses. It’s hard to assess an annual savings for the real estate savings. However, to build comparable space would cost $400/sq ft vs. putting it in $100/sq ft spaces. Using the hypothetical example and 20-year ownership yields an avoided cost of approximately $7,500/year. However, the real benefit is having more available space in the most volatile portion of the hospital.
Lastly, if you build it, the maintenance personnel will come. Providing a centralized UPS system lets the staff focus on learning one type of UPS system, which assures predictable results whenever the equipment is operated in an environment that promotes constant attention. It also keeps the required preventive maintenance activities out of the high-acuity portions of the hospital, which keeps the staff satisfaction scores high.
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