Off the Grid: Electricity at the Maine Huts and Trails Flagstaff Lake Hut Fred Bower and Danqing Zhang Joules to Dollars: Advisors Prof. King (Chemistry) and Prof. Donihue (Economics) What they Needed: The Flagstaff Lake hut is a lodge that accommodates large groups during the winter and summer months who are using their extensive trail system. Their hut sits on a peninsula on Flagstaff Lake, completely off the grid for all electrical, plumbing, and heating sources. With respect to electricity, they are operating a lodge with the equivalent electrical needs of a small hotel, requiring thousands of kWh of electricity annually. It is also important to note that the hut needs electricity whenever there is a need, so the hut must be able to produce electricity on demand, or must have a method of electricity storage. Options: Options 1: Propane Generators: If the hut were to run multiple generators, this method would provide electricity on demand in a reliable manner. Propane however, is not sustainable, and difficult to get to the hut. Option 2: Solar Panels: This method provides electricity in a clean, sustainable fashion. However, for peak loads of electricity the solar panels cannot keep up. In other words, if the sun is not shining, there is no electricity. Option 3: Solar Panels with Batteries: Using a combination of solar panels and batteries, the hut could now provide storage of electricity for nighttime and cloudy days, as well as peak loads. Batteries however are expensive, bulky, and have a fixed lifetime. Option 4: Hydroelectric: Given the proximity of the hut to Flagstaff Lake it was considered by the Maine Huts and Trails to engineer some kind of reservoir that could power a turbine in a small dam to provide energy for the hut. This idea proved difficult and was quickly abandoned. Option 5: Wind Energy: Also given the location, Maine Huts and Trails also looked into wind energy. A wind turbine could capture the wind coming off of the lake and power the hut. Given data on the wind speeds for this location, however, this idea too became obsolete quickly. How it Works and How Well: Solar Panels work utilizing the properties of semiconductors. In a solar cell, there are two layers of silicon. Silicon has a crystal lattice structure, which can be “doped” with phosphorus or boron. The Silicon doped with phosphorus creates what is called an N-type semiconductor. The Silicon doped with Boron creates a P-type semiconductor. When these two are layered together, their properties as semiconductors create “holes” where electrons can move to and from. When photons, energy from the sun, hit the silicon, electrons are energized and move from the Boron doped layer to the Phosphorus doped layer. This motion of electrons in one direction causes the creation of a current which can be captured to generate electricity. The combination of solar panels at the Flagstaff hut can generate a peak of 5.6 kW. The hut is usually able to generate a substantial fraction of its electricity through solar, however, on average they consume an additional 400 gallons of propane to run the generator annually. The system has been successful in the first five years of this hut’s life, however, there are many places where the hut can be improved. Firstly, the inverter in this system is only 80% efficient, meaning that 20% of the electricity that the panels generate is lost due to DC to AC conversion. The hut has looked into updating this, however, it is a substantial upgrade for slow payback. Additionally, the expensive front end cost of this system and building the hut has had slower paybacks than anticipated. After five years of operation, the hut has only recovered 50% of this cost. And although successful, this deficit of capital has made it difficult to expedite the proposed expansion of the Maine Huts and Trails trail system. With that said, Maine Huts and Trails still has the goal to expand to a total of 12 huts connected by more than 180 miles of trails. Why?: At the Maine Huts and Trails huts, there is a focus on sustainable and efficient energy consumption. Utilizing solar power allows the hut to accomplish this goal. The hut choose to pair it with a set of batteries, as the majority of demand comes at night when the sun is not out. By also using a generator the hut can keep up with demand and ensure that guests are comfortable. As an investment, this combination was a compromise between the attraction of sustainable energy and the reliability of fossil fuels. What they Choose: In the end, their solution used an array of solar panels and a tracking panel connected to 24, two volt lead acid batteries. This solar system works in tandem with one propane generator. Because the solar system alone can only charge the batteries to a base rate of electricity storage, the propane generator picks up the remaining electricity as well as taking care of peak demand. While the solar system was quite expensive it allows the hut to have a sustainable energy source that cuts down the demand for fossil fuel electricity generation tremendously. For more Visit: Our Class Website at Maine Huts and Trails Website at Outback Power’s Solar Systems at