A Feasibility Study of Potential Energy Savings

at the Pettit National Ice Center (PNIC)

Revised Quarterly Progress Report

Dr. Kevin J. Renken, Associate Professor

Dr. John R. Reisel, Associate Professor

Mr. B. Andrew Price, Instructor

University of Wisconsin-Milwaukee

Mechanical Engineering Department

Energy Conversion Efficiency Laboratory (ECEL)

3200 N. Cramer Street

Milwaukee, Wisconsin 53211

USA

Tel.: (414) 229-5755; E-mail: renken@uwm.edu

Tel.: (414) 229-4671; E-mail: reisel@uwm.edu

Tel.: (414) 229-2269; E-mail: baprice@uwm.edu

Part of this project involves making recommendations on alternative electricity generation techniques that may be employed at the PNIC in an attempt to lower electricity costs at the facility. Several local generation techniques are being considered and include the following.

1) Wind Power

An initial analysis of power production using wind energy has been performed. The initial analysis is based on estimated average annual wind speeds for Milwaukee, Wisconsin. The average wind speed for Milwaukee is based on a wind classification of 3, as shown in Fig. 1. A wind classification of 3 relates to average wind speeds of 6.7 m/s. The average wind speed is converted to bins of wind speed using a Waybill distribution (Rohatgi, J.S., 1994, Wind Characteristics, an Analysis for the Generation of Wind Power, Alternative Energy Institute, West Texas A&M University). The bins of wind speed are compared to the wind turbine power curves to estimate the possible power that could be produced at the site in a year's time. For example, a Zond 750-50 wind turbine would produce 1,150,000 kW-h of power in one year with an average wind speed of 6.7 m/s and a typical Weibull distribution. The energy estimation will be improved by examining the site to determine the effects caused by local terrain, and comparing the energy demand with the time of production.

Fig. 1. Average wind speed classification for Wisconsin.

The installation of a wind turbine at the PNIC to offset electricity costs is seen as a potentially attractive option. The relatively flat, unobstructed grounds near the facility, coupled with the proximity to Lake Michigan, which induces substantial localized winds, presents a site that offers a number of benefits for the use of wind power. As wind turbines are relatively inexpensive pieces of electricity-generation equipment, this option has moved to the forefront of our considerations.

In addition to the advantages listed above, the use of a wind turbine at PNIC could encourage more installations in the state to use wind power. The high visibility nature of a wind turbine just off of I-94 would provide a substantial amount of exposure for the technique.

One concern that often appears when a wind turbine is to be installed is the noise of the equipment. However, with the large amount of nonresidential area near to the facility, the siting of the equipment should allow for the minimization of the disturbance to the population in the surrounding area.

A disadvantage of wind power is that it is not constant. Therefore, wind power would not completely replace the consumption of utility-produced electricity. Further analysis of the site data will allow us to determine the cost savings possible even with sporadic wind power generation.

2) Solar Energy

Initial assessment of the PNIC site for the use of solar power suggests that the site is not ideally located for substantial electricity production from photovoltaics. The availability of sunny and mostly sunny days, when photovoltaic electricity production is at its highest, is moderate at the site. In comparison, wind energy is much more readily available than solar energy.

However, the PNIC facility does offer a large rooftop space which could be used for the installation of a large array of photovoltaic cells. Therefore, on sunny days, a substantial amount of electricity could be generated on site from solar energy. Further study is planned to determine how the economics of this will appear in a typical year.

3) Fuel Cells

It has been popular to tout the advantages of fuel cells for electricity generation in recent years. Fuel cells have been pushed as a clean power alternative. In addition, as non heat-engine power generation devices, the efficiency of the fuel cells is not limited by the familiar Carnot expressions which impose a Second Law of Thermodynamics limit to the efficiency of conventional power plants. The combination of potentially CO2 emission-free electricity generation and very high efficiencies have caused much focus to be placed on the development of fuel cells recently.

Unfortunately, the reality has not yet caught up to the hype for fuel cells. Currently, fuel cells still suffer from problems related to the poisoning of the catalyst with carbon. As the most common fuels are hydrocarbons, the use of hydrocarbons in fuel cells typically require a reformer to separate the hydrogen from the carbon, directing the hydrogen to the fuel cell for power generation. During this process, something must still be done with the carbon to prevent it from contributing to CO2 emissions. In addition, the reformation process requires energy, which uses a considerable portion of the electricity produced by the fuel cell, thereby reducing the overall efficiency. A different source of hydrogen to power fuel cells at PNIC would avoid this problem, but such a source is not readily available. Fuel cells, though, could be sized to satisfy the entire electrical needs of the PNIC, and would not be subject to fluctuations in weather conditions. At this time, further investigation is needed to determine the feasibility of fuel cell utilization.

4) Micro Gas Turbines

Micro gas turbines are small-scale gas turbine electricity generation systems that are designed to provide power for factories, small businesses, or similar settings. These devices use modern gas turbine technology, similar to that found in large-scale gas turbine power plants, but at a small scale suitable for satisfying localized power needs. These systems have good efficiency, and have the advantage of removing the facility from the utility power grid. This would greatly reduce, or eliminate, the PNIC electricity costs. However, the natural gas bill would increase, as the devices operate by burning natural gas. Therefore, a recommendation on the use of micro gas turbines will be based on a careful economic analysis, to determine if any operational costs savings exist, and if they offset the capital equipment cost.

Future Analysis

As described above, the focus of this portion of the project will be the economic viability of each of these technologies. There is no question that if the meteorological conditions are favorable enough, the electricity costs at PNIC can be reduced, although not eliminated, by the use of one or more of these technologies. The determining factor in the recommendations is whether the operational cost savings from these technologies justifies the capital costs of equipment installation.

If these technologies do not appear to be economically viable, more focus will be placed on micro gas turbine. Finally, if micro gas turbines are not a feasible option, stationary fuel cell technology will be considered. As discussed above, while both of these technologies have the potential to remove eliminate the need to buy any electricity from the utilities, they do add fuel costs.

Fig. 2. Photo of snow pit.

Fig. 3. Photo of PNIC compressor system.

Fig. 4. Photo of rooftop condensing tower.

Fig. 5. Photo of current HVAC ductwork at PNIC.

Fig. 6. Photo of PNIC HVAC room.

Fig. 7. Photo of nearby Wisconsin State Fair Park Youth Center.