Missoula Fire Station No. 4 is the first in Montana to be partially solar powered. (I’d also be willing to wager that it is the first municipal station to be grid intertied in the country, but I'd also be delighted to find out I’m wrong.)

It is estimated that the system will produce approximately 6,500kwh of electricity each year. The system is primarily a grid intertie system, with battery backup. Power stored in the battery bank is used only in the event of a power outage and powers circuits critical for the station’s operations. Best of all, we think that it is firefighter proof (meaning it is indestructible and low maintenance.)

The system was funded through a $50,000 grant from the Universal System Benefits Charge, administered by Montana Power Company.

Sunelco of Hamilton, Montana, installed the system. It became operational in March 2001. The grant proposal basically wrote itself. The combination of a good solar site, and a classroom in the building, made the fire station a good candidate.

The savings in energy costs benefit the local taxpayers, and we can train firefighters how to work safely around renewable energy systems. As these systems become more prevalent, firefighters will need to recognize when a building’s electrical circuits are de-energized. Other agencies such as schools and folks in the electrical trades can also use the classroom to get familiar with solar components.

The system is wired in a 48-volt configuration. (See the PV System Key below). The system consists of 40 Kyocera 120 watt panels, 32 of which are roof mounted and 8 that are pole mounted on a Zomeworks tracker. Although it is questionable whether or not a tracker makes sense in Montana, we wanted to demonstrate various components and have some of the panels accessible without going up on the roof.

Power is routed through four RV Solar Boost 3048 charge controllers, which keep the batteries topped off. The majority of the power is then inverted to 120-volt AC through a Trace 4048 inverter and made available for the station’s demand. When electricity generated is in excess of the station’s demand, the inverter sends the power to the utility grid, causing the electrical meter to spin backwards. This is a rare occurrence, as the fire station was designed in times of regulated and plentiful electricity.

The station uses fluorescent lighting and compact fluorescent bulbs, but it uses electric heat in the public bathrooms and has a complex HVAC system. I just hope that I’m around when Missoula designs its next station!

The battery bank consists of 12 Surrette 4KS – 21PS 4-volt batteries wired in series for 1104 amp hours at 48 volts. It will easily supply circuits critical for station operation – including door openers, radios, some lighting, and the computer – for up to six hours. When the inverter senses a power outage, it draws power from the batteries as needed. In the case of an extended outage, the station relies on an auxiliary diesel generator.

Missoula is a pretty green city, and the city government and administration mirror that in their policies supporting renewable energy, conservation, and efficiency. The Mayor’s car is a Toyota Prius, but you’re just as likely to see him about town on foot or on a bike.

Missoula Fire Department welcomes visitors to stop by to see the system during daytime hours, and when the crew is in quarters. Please don’t expect the on-duty firefighters to answer all your questions about the system. A handout sheet is available at the station, and a system component diagram is posted in the inverter room.

1. AC kWh meter – Displays the energy production of the PV system
2. Inverter AC input/output disconnect & bypass breaker box – Provides a means to disconnect the AC input & output to the SW4048 inverter. This disconnect also provides an easy manual means to route utility power around the inverter (in the case of a system failure) and supply 120 VAC power to the AC sub panel.
3. Trace SW4048 inverter – Converts DC power from the 48V solar array and/or battery bank to 120 VAC power to be used in the 120 VAC sub panel located in the utility room behind the office
4. Trace DC175 disconnect – Provides the NEC required main disconnect and overcurrent protection for the circuit connecting the battery bank to the SW4048 inverter.
5. Trace PVGFP3 ground fault protection device - Provides the NEC required ground fault protection for a roof mounted solar array.
6. RV Power Products SB3048 Maximum Power Point Tracking (MPPT) charge controller – This controller maximizes the output from the solar array while preventing the batteries from being over charged by the solar array.
7. RV Power Products SB3048 Maximum Power Point Tracking (MPPT) charge controller – This controller maximizes the output from the solar array while preventing the batteries from being over charged by the solar array.
8. RV Power Products SB3048 Maximum Power Point Tracking (MPPT) charge controller – This controller maximizes the output from the solar array while preventing the batteries from being over charged by the solar array.
9. RV Power Products SB3048 Maximum Power Point Tracking (MPPT) charge controller – This controller maximizes the output from the solar array while preventing the batteries from being over charged by the solar array.
10. Surrette battery bank consisting of twelve 4KS-21PS 4V 1104 amp-hour batteries – This battery bank is maintained at a float charge by the solar array and can provide backup power to the 120 VAC sub panel in the event of an extended utility power outage.
11. Outdoor Solar AC disconnect – Provides the NEC required AC disconnect in between the utility main AC panel and the SW4048 inverter’s AC input. This AC circuit is bi-directional (input & sell) so this disconnect would allow a utility worker to quickly disconnect the AC power that the PV system is sending back to the main AC panel if they need to do any work on the line.
12. 120 VAC sub panel – New sub panel installed in the room behind the office that contains the critical loads that the system powers in the event of an extended utility outage.