In the fall of 2008, Michaels Energy moved into the second floor of the 100 year old, former downtown department store, Doerflinger’s. The space was completely renovated including refurbishing the original maple floor, repairing plaster, replacing glazing in the original windows, and installing an efficient heating and cooling system with condensing boilers, water-cooled chiller and variable frequency drives on nearly all pumps and fans. By mid-winter, Michaels’ gas bills showed literally about one quarter of the gas consumption that the third floor was experiencing – 299 ccf versus 1,228 ccf. The third floor has nearly identical floor space (14,000 square feet), glazing, and exterior exposure and a similar variable air volume (VAV) heating and cooling system. The building owner asked Michaels to investigate the cause of this apparent wasted energy. Knowing the system type, the target before investigating was excessive VAV box reheat.
The third floor included a substantial data center with waste heat available for free heating of the third floor. Within minutes, Michaels had determined that the distribution system for that heat recovery system was causing the adjacent space to “over heat”. This was driving the entire central system for the floor into cooling to cool that space. Not only was this resulting in excessive zone reheat for all the other zones, it was canceling the heat recovered from the data center.
The solution: take the temperature sensor serving the adjacent space off the system. Disable it.
Gas consumption immediately plunged. The chart below shows gas consumption per heating degree day. The green lines represent the post implementation gas consumption. The other lines present gas consumption for months/years prior to “implementation”. Gas savings are approximately 50%. Payback period: instantaneous. This prompted the tenant of the floor to replace their control system to provide functionality that is more similar to the Michaels’ system. This generates even greater savings.
 Michaels and the third floor share chilled water, which is not sub-metered. Therefore, electric savings are much less discernable.
Tri-County Electric, a rural Minnesota electric cooperative investigated the 144,000 square foot Caledonia High School, in Caledonia, Minnesota, for energy saving opportunities in response to the District’s concerns regarding energy costs and a pending rate increase. The facility was approximately 4 years old and includes a ground source heat pump system. Tri-County identified potential savings with the water circulating system and referred the District to Michaels for further assistance.
Michaels conducted a walk-through investigation to identify potential opportunities and gather information for proposing the next steps. The pumping system indeed provided opportunity, but so did makeup air units, and ventilation controls. Michaels conducted the feasibility study and developed three primary energy saving measures:
Convert the primary/secondary pumping system, a parallel pumping system, to series only. This included removing one 100 hp circulating pump that operated at 60Hz altogether, installing isolation valves on heat pumps and interlocking them with the heat pump compressors, and controlling the remaining pump with circulating loop static pressure.
Revise the control sequence for makeup air units to allow the discharge temperature to float rather than continuously providing 70F air to downstream heat pumps. This provided an opportunity to eliminate heating at the unit and then cooling downstream – simultaneous heating and cooling, which is virtually ubiquitous when air handlers serve multiple zones.
Revise the control sequence on CO2 demand controlled ventilation to 700 parts per million above ambient CO2 levels rather than 700 ppm, absolute, which is only about 300 ppm above ambient. This resulted in a substantial reduction in ventilation volume and associated conditioning energy.
Michaels provided control sequences and implementation documents for the project and later provided functional performance testing of the measures.
Energy savings for these measures was predicted to total 30% of the building’s energy consumption with a 3.6 year payback. Projects were implemented in the summer of 2007. Comparison of twelve months pre and post installation indicates a 40% reduction in energy consumption for a 2.7 year actual payback. In addition, a billing error was identified at the outset of the feasibility study resulting in an instant $5,000 refund from the utility.
As part of the project, the building earned the ENERGY STAR®, increasing its ENERGY STAR Portfolio Manager score from 37 to 93.
Michaels Energy, with funding assistance from Focus on Energy, teamed with Nestle Nutrition to incorporate energy efficient design features into Nestle’s production facility addition in Eau Claire, WI. The plant will produce infant formula from a liquid feedstock.
Michaels met with Nestle stakeholders to gain an understanding of the production process from receiving through packaging. Energy efficient upgrades were identified in this kickoff meeting. Additional measures were developed as the process was further studied by Michaels Energy staff in La Crosse. A second meeting with Nestle was held to discuss the potential design alternatives and select projects for investment-grade energy analysis.
Measures identified and analyzed include:
- Heat recovery from a continuous drying process to preheat process water with recovered heat further used to heat makeup air for the facility.
- Heat recovery from a batch process using a combination of large silos of water serving as the heat sink and heat exchangers for preheating and precooling product.
- Non-Condensing boiler stack heat recovery for the new boiler and a downstream condensing economizer to recover heat from both the new process boiler and existing process boiler.
- Outdoor air supply for air compressors and purgeless air dryers.
- Variable frequency drive for new boiler burner fan.
- Variable speed ammonia compressors used for making process chilled water.
- Floating ammonia compressor head pressure control.
- Thermosyphon free oil cooling for ammonia compressors.
- Process cooling tower heat recovery used for plant space heating and receiving area snow melt.
- Variable speed cooling tower fans and energy efficient motors.
The above measures combine for $1.2 million in annual energy savings, resulting in a combined simple payback of 1.4 years using trailing energy costs. This includes savings of 1.3 million therms, 1.4 million kWh, and 1.7 MW.
Larry Willi, Senior Facilities and Utilities Engineer for Nestle, plans to use Michaels and Focus on Energy programs for pending projects in the future.
The Energy Solutions Center, a Washington, DC-based non-profit organization promoting the efficient use of natural gas, contracted with Michaels Energy to produce a report on the energy-saving potential, best practices, and persistence issues surrounding retrocommissioning projects and programs.
As part of the study, Michaels Energy shared its experiences, lessons learned, project data, and recommendations for retrocommissioning (RCx) programs with specific emphasis on natural gas savings potential.
The natural gas savings potential for RCx is very attractive and significant. For buildings served by natural gas, monetary natural gas savings account for about 43 percent of the total savings for all fuels, even during periods of low natural gas prices.
To learn more about RCx and the major gas-saving measures found during the study, view the full report here. For further questions, please contact Jeff Ihnen at (608) 785-1900 or JLI@MichaelsEnergy.com.
Weinberg Investments faced a challenge with an aging heating and cooling system for their 80-unit high-rise apartment complex, built in the 1930′s. In addition to being energy-inefficient, the heating and cooling system could not meet space-conditioning requirements for the facility’s senior residents.
The building had a “two-pipe” heating and cooling system to minimize first cost when it was installed in the early 1980s. The entire building was either in cooling mode or in heating mode at one time, with one switchover in fall and one in spring. This created temperature control problems and persistent com-plaints from the residents.
Michaels Energy Explores Options
Lew Weinberg, proprietor of Weinberg investments, retained Michaels Energy to explore converting the building’s heating and cooling system to a geothermal heat pump system.
The existing heating and cooling plant consisted of gas-fired steam boilers and an air-cooled chiller. The boilers made hot water, which was circulated to fan-coil units in the apartments and makeup air units serving the corridors. When the system was in cooling mode, the chiller provided chilled water through the same distribution system.
Feasibility Study Offers Results
Michaels completed a feasibility study to examine the cost and savings benefits of converting the system to geothermal heating and cooling. Converting the building’s inefficient T12 and incandescent lighting systems to efficient T8 fluorescent and compact fluorescent technologies was also analyzed as part of the study.
The study results provided Mr. Weinberg with the information and confidence he needed to pursue implementation.
Following the study, Michaels’ design team provided design services to implement the project. Key design concepts included:
- An open-loop geothermal design was used for this downtown location because sufficient area was not available for a closed-loop well field.
- “Tower” heat pumps replaced existing fan-coil units in the existing cabinets to avoid carpentry and architectural work, minimizing implementation cost.
- Water-to-water heat pumps were used for heating and cooling makeup air units serving the corridors. This was a key design element as it allowed the steam boilers to be retired and negated the need for a smaller inefficient cooling source for the make-up air.
After the new geothermal system was in operation for about two years, the actual results were impressive. Utility bills showed a reduction in energy costs that matched the predicted results almost exactly.
In addition to energy savings, the building has a new heating and cooling system that will provide years of reliable operation. The temperature control / comfort problems have been eliminated and each resident can efficiently achieve heating or cooling as they desire all hours of the year.
The Housing Authority of La Crosse retained Michaels Energy to complete energy audits for its seven high-rise facilities, four low-rise developments, a preschool, and the Housing Authority Administration building. These energy audits meet the federal Housing and Urban Development requirements for energy audits.
Michaels provided cost and savings estimates for the identified measures. The intent of these estimates is to provide a magnitude of savings potential and approximate costs to achieve the savings. The estimates will help the Housing Authority to decide whether to pursue certain projects and to plan for future facility upgrades.
The Minnesota Department of Commerce retained Michaels Energy to complete a study on the performance, emissions, and economic analysis of Minnesota geothermal heat pumps.
The primary purpose of this project was to determine the difference in energy consumption, user costs, and amounts of pollutants and carbon dioxide emissions for Ground Source Heat Pumps (GHPs) as compared to conventional Heating, Ventilation and Air Conditioning (HVAC) systems in Minnesota residential, commercial and institutional buildings used for heating and cooling air and water heating, and; identify current installations of GHPs, available financial incentives, manufacturers and installers, economic development potential, and barriers to more widespread, cost effective use of the technology in Minnesota.
Alliant Energy designated Michaels Energy to develop an efficient grocery store that would break the conventional design mold. Grocery stores have for decades used inefficient rack refrigeration systems because they are “reliable” and provide adequate backup in case of compressor failure. The systems are inefficient compared to design features employed by industrial refrigeration systems. Why can’t industrial refrigeration design elements be incorporated into supermarkets to make a quantum leap in energy efficiency? Michaels investigated.
Starting with an energy efficiency report provided by another utility, Michaels chose to take aim at the biggest energy user in any grocery store: the refrigeration system. Alliant Energy and Michaels presented Hy-Vee with a refrigeration system design that looks more like an industrial design than a conventional run-of-the-mill rack system. The design incorporates:
- Open drive reciprocating compressors with step unloading. There are two compressors each for three suction temperatures, -30F, 20F, and 35F.
- The low stage (low temperature) compressors discharge to the suction side of the high stage (high temperature) compressors. This two-stage compressor plant design saves significant energy.
- The compressors discharge hot refrigerant gas to an evaporative condenser on the roof. The evaporative condenser has a variable speed drive to save energy. But more importantly, the evaporative condenser allows condensing temperature and pressure to be as low as weather conditions will allow. This greatly reduces compressor energy consumption.
The industrial-type refrigeration system uses approximately 50% less energy than the conventional rack system, saving nearly 1.5 million kWh per year for a typical 80,000 square foot store. This is a reduction of about 30% for the entire store’s energy consumption, which includes lighting and HVAC. Additional measures including demand-controlled ventilation, kitchen hood exhaust controls, and efficient evaporator fan motors and fan blades were identified and implemented for an additional 800,000 kWh in annual savings.
The Wilson College Complex for Science, Mathematics and Technology is a 76,500 square foot facility housing teaching and research labs, classrooms, offices, an auditorium and a natural history museum. Wilson College is committed to environmental sustainability, and that commitment guided the design of the science complex, including the decision to seek LEED® certification. Michaels Energy, as a subconsultant to Performa Higher Education, provided HVAC, electrical and plumbing engineering, and served as the LEED® Accredited Professional and Project Administrator.
Energy Efficiency and Sustainability Features
Laboratory facilities require large amounts of fresh air ventilation and tight control of temperature, humidity and room pressurization. To satisfy these requirements while maximizing energy efficiency, Michaels researched alternatives to the typical variable air volume reheat systems typically used to heat, cool and ventilate these facilities. This resulted in the decision to incorporate a dedicated outdoor air system (DOAS).
The DOAS uses two energy recovery wheels, along with heating and cooling coils, to pre-condition 100% outdoor air to room-neutral conditions. Under most conditions, about 70% of the ventilation air heating, cooling humidification and dehumidification is provided by heat and moisture transfer between the exhaust and outdoor air streams.
This preconditioned air is distributed throughout the building via corridor ceiling plenums, and is drawn into individual laboratories to offset fume hood and general exhausts. Local fan-coil units in each space trim the space temperature as required. A digital control system adjusts ventilation based on occupancy, sensed through a combination occupancy sensors, lighting operation and fume hood sash movement.
Additional energy efficiency and sustainability features include:
- Daylighting in perimeter offices, combined with multi-level indirect lighting
- High efficiency condensing boilers
- Water-side free cooling in the winter using dry fluid coolers
- Dual-flush toilets, waterless urinals and ultra low-flow faucet aerators
- Low-emitting adhesives, finishes and carpet systems
- Solar water heating
An additional benefit to Wilson College for choosing to incorporate a dedicated outdoor air system, as well as other efficient technologies, is the opportunity to partner with West Penn Power. The West Penn Power Sustainable Energy Fund is helping Wilson College fund the DOAS as well as the solar water heating system.