Fuel Cells

A fuel cell converts the chemical energy from a fuel into electricity through a reaction with oxygen (or oxidizing agent).
credit: Lars Plougmann

Batteries are a well-known type of electrochemical reaction. Batteries contain chemicals, which are mixed to create a reaction. When the chemical reaction is complete, the battery dies and does not produce any more electricity. While fuel cells are also an electrochemical reaction, they are different because when chemicals are constantly input, the electrical flow produced is continuous.

Fuel cells are beneficial because they do not emit any greenhouse gases or air pollutants during operation. If hydrogen is the fuel, the only byproducts are water and heat. They can achieve high efficiencies - when heat is combined with power production, fuel cells can reach over 80% efficiency.

Fuel cells can be extremely efficient in a wide variety of applications, such as fuel cell electric vehicles, laptop computers, power generation for commercial and residential buildings, and combined heat and power systems.

Free LEED Exam PreperationTypes of Fuel Cells

There are many types of fuel cells, though they are typically distinguished by the type of electrolyte, or fuel, that they use. For example, alkaline, polymer electrolyte membrane, phosophoric acid, solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MOFC) are all types of fuel cells.

According to the Department of Energy, polymer electrolyte membrane, phosphoric acid, molten carbonate and solid oxide fuel cells can all be used for distributed generation, though SOFC is the most efficient (at 60%). MCFC and SOFC can be used for electric utilities, while polymer electrolyte membrane fuel cells can be used for transportation and specialty vehicles. Alkaline fuel cells are primarily used for military and space operations.

Most fuel cells, regardless of the fuel type, are composed of four parts: a fuel cell stack, a fuel processor, current inverters and conditioners, and a heat recovery system.

Residential Fuel Cells

Fuel cells for residential applications are currently limited. Typically, a home fuel cell is a micro combined heat and power unit, or a microgenerator, which simultaneously generates heat and power from natural gas, propane, or biofuels. The system is much more efficient than traditional grid electricity or fuel combustion.

There are federal tax credits currently available for residential fuel cells and microturbine systems in new and existing homes. The tax credit is for 30% of the cost (including installation costs), for up to $500 per .5 kW of power capacity. The fuel cell must be at least 30% efficient and must have a capacity of at least 0.5 kW to qualify for the tax credit.
While the residential market is limited, the tax credit expires in the end of 2016, which gives the sector time to expand before its expiration.

Bloom Box

Bloom Energy is the most well-known company for modern fuel cell technology, with companies like Google, eBay and Wal-Mart using their technologies for electricity. Based in Sunnyvale, California, the company is best-known for the Bloom Energy Server, more commonly known as the "Bloom Box", which is one of the most popular fuel cells on the market.

The Bloom Box is a solid oxide fuel cell (SOFC) that can run on a wide variety of fuel inputs, making it extremely flexible. They can run on a variety of fuels, including fossil fuels, such as natural gas, or renewable energy, such as renewable biogas. It is low cost because it uses common sand-like powder instead of precious materials. With 60% or more electrical efficiency, it has almost double the efficiency of coal-fired power plants, which are 33% efficient. Part of this is because it runs at high temperatures without needing maintenance or repair. Fuel cells are also not grid connected, so they avoid 7-15% losses from grid transmission inefficiencies.

Bloom Boxes provide 200 kW of power, which is enough to power 160 homes or an office building.

While Bloom Boxes are currently available and popular in the commercial market, they are not yet available for homes. However, the founder, K.R. Sridhar, said a few years ago that a residential Bloom Box would be out in 5-10 years and would cost under $3,000 (though it may take two to power a traditional U.S. house).

The Future of the Fuel Cell Market

The fuel cell market is currently limited by a number of factors, including cost, reliability, and improved heat recovery systems.

Cost. Fuel cells are expensive and need to meet the industry standards to be competitive. The Department of Energy says that stationary fuel cell systems must reach an acceptable price point of $400–$750/kW, or up to $1000/kW for initial applications.

Reliability. Additionally, fuel cell systems will need to have the same reliability and durability standards as their competing technologies. According to the Department of Energy, they need to achieve 40,000 hours of reliable operation at -35°C to 40°C.

Heat Recovery Systems. Fuel cells that are used in combined heat and power systems (CHP) are called PEM fuel cells. They have a low operating temperature, which limits the efficiencies of CHP systems. PEM fuel cells will need to develop higher operating temperatures, which could bring CHP efficiencies over 80%.


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