EERE Success Story—Using Advanced Modeling Tools to Make More Efficient Fans

The Energy Department’s Building Technologies Office (BTO) is researching opportunities to make homes safer and more efficient through the Small Business Innovation Research program (SBIR).

Mechanical Solutions, Inc. (MSI), a small business, is working to increase the energy efficiency of a radon mitigation technology that helps improve indoor air quality and reduce wasted energy.  Using Computational Fluid Dynamics, the radon fan was redesigned and is estimated to reduce energy consumption by a minimum of 25% compared to state-of-the-art units. After completing a successful Phase I SBIR for the Building Technologies Office, Mechanical Solutions was recently awarded a Phase II SBIR contract. This will enable a more detailed and optimal design to be developed, tested, and prepared for market with MSI’s radon fan commercialization partner, Fantech.

Radon is a radioactive gas that comes from the soil, causing an estimated 20,000 deaths per year in the United States – and is the second leading cause of lung cancer after smoking.  Radon can enter homes through cracks or openings in the foundation; the difference in air pressure between the inside of a home and the soil around it can act as a vacuum, sucking radon gas inside.

When radon breaks down in soil, it emits atomic particles into the air we breathe. When diluted in open air, radon does not present a health risk. Inside, however, it can build up to dangerous levels that increase the risk of lung cancer. Fortunately, mitigation technologies that detect and remove radon have been proven effective at reducing this harm.  The Environmental Protection Agency (EPA) estimates approximately 6 million homes suffer from elevated radon levels, with only 600,000 having mitigation systems installed. 

The EPA and the Surgeon General recommend testing for radon and reducing it in homes that have a high level to reduce the risk of lung cancer. Radon reduction systems can reduce radon levels in homes by up to 99 percent, often for the same cost as other common home repairs.

Radon fans are one technology used to ventilate buildings and reduce the health risks of elevated radon levels.  These fans run continuously to pull radon and air from either the occupied space or the area beneath the foundation slab.  While effective at their primary task, there is a lot of room for improvement for energy efficiency. 

Radon fans can use nearly five times the electric energy that a common, small-size highly efficient fan and motor would use. They typically run at a maximum 20% efficiency. Across the 6 million fans the EPA estimates are required for mitigation, there is a large amount of wasted energy (equivalent to between 1 to 2 GW-hrs) and a substantial annual cost to the consumer.   

MSI determined that Computational Fluid Dynamics (CFD) Analysis was perfect for redesigning radon fans as the software allowed easy access to specific areas of improvement, and enabled the engineers to simulate the momentum, energy, and thermal state of complicated gas flows and systems.  Prior to the advent of this software and advanced high speed computers, aerodynamics engineers required expensive and time-consuming wind tunnels and machine testing to iteratively resolve all aspects of a proposed design. 

MSI is the first to apply CFD analysis for this application, realizing it would be a perfect fit to analyze a compact, but complex flow system. By using the CFD software, aerodynamics engineers are able to explore “out of the box ideas” while guiding engineers to specific areas of improvement. These ideas can be linked with other engineering software such computer-aided drafting, also known as CAD, in order to find the most robust and cost-effective solution that maintains current geometry critical to the manufacturer and improves energy performance.

To improve upon the design, MSI scanned data from a standard market product and input it into a model to determine a current baseline. Because radon fans are always on, it presents both an opportunity and a challenge from a design standpoint: the MSI team investigated six different fan models to find the optimal design that was energy efficient, had high performance, and its components could be assembled within the casing of traditional fans to allow industry to quickly take-up the new design.

By using CFD analysis, MSI was able to identify sources of inefficiency such as discharge of the fan system and compare those baseline measurements against the CFD of the newly designed fan to double check design optimization had occurred. According to Dr. Edward Bennett, MSI’s Vice President of Fluids Engineering, "CFD continues to prove its value as a cost-effective and superb optimization tool, and we look forward to yet another validation of modeled results in the testing phase of the program."