Last week, I joined a panel of experts for a live discussion about fuel cells, covering everything you needed to know about this clean energy technology. We asked you to submit questions in advance and during the event, and we received more questions than we could answer. So now I am answering some of your questions that went unanswered.

Can you discuss fuel cells for residential and commercial buildings and their cost? 
— from TydeFarm and Jim B., both via email

The cost of fuel cells for residential power is expected to decrease in the coming years due to investments in research and development made by the Energy Department and industry. In general, fuel cell costs are still higher than other residential power options, but they provide high reliability and resiliency. Costs can range from $2,300 per kilowatt to $4,000 per kilowatt, excluding installation. That means for a 5 kilowatt residential unit, it can cost up to $20,000.

Fuel cells for commercial buildings are more widespread and costs range from $3,500 per kilowatt to $5,500 per kilowatt, depending on the type of fuel cell and application. In addition to base load power and heat for buildings like hospitals, hotels and industrial plants, fuel cells are being used in telecom and data center applications for backup power — illustrating the dependability of fuel cells and willingness of businesses to rely on fuel cells for mission-critical power.

For more on the Department’s cost targets, check out our Multi-Year Research, Development and Demonstration Plan.

Onboard fuel reforming for fuel cell vehicles can start in under four minutes. A refueling infrastructure with natural gas or methanol seems easier, so why choose hydrogen?
— from Dave Higdon on Twitter

Until about 10 years ago, the Department had an active program in onboard reforming — the ability to convert a fuel into hydrogen — for vehicle applications. However, we decided to focus on direct hydrogen fuel cells for transportation applications (and thus a hydrogen fuel station infrastructure) based on the low probability of achieving key metrics that would make onboard reforming viable, such as a start-up time of 30 seconds, the ability to go from 10 to 90 percent power in one second, and a cost of less than $10 per kilowatt.

In addition, onboard reforming was not expected to result in fuel efficiency that is significantly higher than that of hybrid vehicles with internal combustion engines, so automakers were not interested in pursuing it.

When there is an option to use biofuel to run cars (which would be cheap, and the technology is already there), why should one be interested in fuel cells to run cars?
— from Navvab KHD on Google+

To meet the President’s goal of reducing greenhouse gas emissions by 80 percent by 2050, the Energy Department is working to cut carbon pollution and petroleum use in the transportation sector through a portfolio of technologies, including biofuels, electric vehicles and fuel cell vehicles. Biofuels are a key part of our strategy, but the total sustainable biomass in the U.S. would not be sufficient for displacing all the petroleum used in the entire transportation sector.

Biofuels from corn and fuel cell vehicles that run on hydrogen produced from natural gas, both can achieve a greenhouse gas reduction on a well-to-wheels basis of about 60 percent compared to today’s gasoline-powered internal combustion engine. However, the added benefit of fuel cell vehicles using hydrogen from renewables, like solar energy, is that they could further reduce emissions by more than 90 percent.

How is the durability of fuel cells during temperature changes? 
— from Omar Delgado via Facebook

For fuel cell vehicles to achieve market parity with conventional vehicles, they must meet durability targets (about 5,000 hours or 150,000 miles) but also function over the full range of operating conditions. Fuel cells can operate at temperatures well below the freezing point to above the boiling point of water and humidity levels ranging from dry to wet. Both very low and high temperatures can impact durability, but our durability testing shows that we’re on track to meet our targets. For more on the technical targets for addressing fuel cells in cold weather, check out the Department’s Multi-Year Research Development and Demonstration Plan.

What is the typical lifetime of a stationary fuel cell? Where are fuel cells manufactured?
— from Laurence Grand-Clement via email

The current operation lifetime of a stationary fuel cell is 40,000-80,000 hours, depending on fuel cell technology. But factors such as application, temperature, contaminants and duty cycle can impact lifetime.

Fuel cells are developed and manufactured all over the world including the United States, Canada, Korea, Japan and the European Union. In 2012 alone, about 6,000 fuel cells were manufactured in the U.S. — double the number manufactured in 2011. For more on the state of the fuel cell market, check out the Department’s 2012 Market Report.

I’d like an update on new fuel storage technologies for fuel cells. What progress has been made in the past years?
— from Alexsandra Guerra on Twitter

The Department’s goal for onboard storage of hydrogen is a 300-mile driving range for fuel cell vehicles. In recent years, we have demonstrated numerous vehicles using high-pressure compressed hydrogen storage tanks with an average driving range of more than 250 miles and for a full size SUV, we have demonstrated a driving range of up to 430 miles on a single fill. However, cost is still a challenge and the driving range must be achievable across the full range of light-duty vehicle platforms without compromising space or performance. As a result, we are looking at new ways to increase the performance and reduce the cost of the carbon fiber composite tanks — a breakthrough that could lower hydrogen tank costs by 30-50 percent.

While the near-term hydrogen storage solution is high pressure compressed tanks, our long-term portfolio is focused on hydrogen storage materials that offer potential for increased capacities, lower pressure and higher system efficiencies. In recent years, more than 400 new hydrogen storage materials have been investigated and catalogued in the Hydrogen Storage Materials Database through our three Material Centers of Excellence.