Over the past 20 years, Bloomington has gone through the process of installing eight backup power systems and seven generators at their water and wastewater facilities. As the City has expanded its facilities, it has included backup power systems in new and existing facilities.
During each installation and upgrade, Bloomington accounted for climate change projections and expected changes in demand at least 10 years into the future. As the population and the local climate are changing, planning based on historical trends and current data is not always sufficient to meet future needs.
When installing its backup systems, the first step was to establish the system capacity and minimum need during an outage. If the grid is down, it would be difficult and costly to provide the amount of power needed to operate at full capacity, so the City of Bloomington needed to determine the appropriate level of backup power capacity. For instance, Bloomington’s water plant during normal operations can distribute 30 million gallons of water per day. The maximum amount the City regularly distributes is around 19 million gallons per day. Using standard engineering calculations, Bloomington determined its critical need at the time for that plant to be 12 million gallons per day.
After determining its critical need, Bloomington hired a contractor to design the backup systems, a task that requires a specialist.
Bloomington made sure to avoid building the backup systems in a floodplain. The consultant, working in partnership with City staff, designed the structures with an open top or in a cool, shaded location, when possible, to prevent the systems from overheating when ambient air temperatures are high. In cases where the cooling options were not feasible, Bloomington installed climate controls.
Currently, all of Bloomington’s backup power systems are fueled by diesel generators. Not enough space was available on-site at any location to host 100 percent alternative fuel sources like wind or solar. However, Bloomington has been adding solar power for some of its backup systems. While there is not enough solar to fully power any one system, the renewable energy source reduces the amount of diesel needed.
When power is lost, Bloomington’s systems turn on the generators immediately to ensure there are no gaps in service. The automatic switches also send alarms to staff to respond as soon as possible to monitor the situation as it unfolds.
For system maintenance, plant operators start the generators around once a month and do a full system test at least annually to make sure the systems are working properly.
The cost for a backup power system varies depending on its size and how much power it needs to generate. Bloomington’s individual systems have ranged from $200,000 to $3 million.
Bloomington has been adding backup power for the past 20+ years in various capacities. Each upgrade takes around a year from the design phase to a finished product, but this can vary depending on the size of the system.