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Sustainable Grid Integration of Distributed and Renewable Resources

UUMC Energy Audit

In an outreach/research/education activity, IGERT Trainees and Affiliates provided a basic energy audit for the University United Methodist Church (UUMC). Projects and team members include:

1. Chiller operation / interface with vendor / age /efficiency, boilers – Estes, Powell, Charlton

2. Air handling / HVAC system, airflow in sanctuary - Tuttle, Upshaw, Cole

3. Building/blueprint analysis, window heat loss - Bourne, Rhodes

4. Lighting (efficiency, modernization), motion sensors - Toliyat, Sriprasad

5. Energy audit / circuit breaker issue / water consumption - Dahlberg, Fares

UUMC Energy Usage Status Report 9/30/11

Lighting

UUMC recently had all of their light fixtures updated.  All of the fluorescent fixtures in the Education Building already have T8 bulbs/ballasts.  Due to their high efficiency, no changes should be made to the lighting in the Education Building.  There are a handful of incandescent bulbs still in operation in the Education Building, but they make up a small fraction of the installed lighting in that building. Changing those would be at the church's discretion and would not decrease the church's energy use significantly.

In the sanctuary, there are a large number of fully enclosed, 40 W incandescent light fixtures on the underside of the balconies. The sanctuary is also lit by two high power halogen floodlights mounted above the altar and a number of incandescent floodlights mounted high in the ceiling. Marc Erck did not know the specific wattage of the halogen or incandescent floodlights.  Marc mentioned that he is unhappy with the current level of lighting in the sanctuary.  Parishioners have complained about their inability to read in low light.  The most direct lighting that could be used for reading comes from the enclosed, 40W incandescent lights on the underside of the balconies.  The fixtures are designed for an incandescent bulb with a maximum power of 40 W.  UUMC could change these bulbs with fluorescent bulbs which provide more light and draw less than 40 W.  This would improve lighting in the church and decrease their energy use by a small percentage.  However, CFLs are generally not designed to work in enclosed fixtures. Their associated electronics must be kept cool.  Furthermore, Marc mentioned that the church would like the ability to dim lighting in the sanctuary.  This further complicates replacing the incandescent bulbs as dimming is more complicated with CFLs.  Energy efficient lighting meant to take the place of high power halogen floodlights and the other incandescent floodlights in the ceiling is still under discussion.  UT could calculate the total kw of lighting and estimate number of hours operated (and when).  Lights that are difficult to access should have long-life bulbs.  However, accessing the high ceiling lights in the sanctuary is not a problem for periodic replacement.

At this time it seems the church's energy use cannot be reduced much by changing lighting alone. There is little gain in efficiency to be realized in the Education Building, and the lighting in the sanctuary is on only 5-6 hours each week and does not make a significant contribution to the church's electricity consumption.  Motion sensors could be added in certain rooms to reduce lighting costs, but these rooms would need to be identified by church staff.

Building Envelope

Upon assessing the state of the building envelope, there are multiple areas that can easily be improved. All doors had weather-stripping issues, some gaps as large as 1/3 inch.  There was also broken glass in several places.  This is a relatively easy, low cost fix that would tighten up the envelope.   The stained glass windows have clear plate glass on the outside, which performs well for storm windows; however, considering the infrequent use of the sanctuary, UT does not recommend decreasing the gap between the stained glass and storm glass, although this would cut down on convective losses between the panes.

The windows on the other building are single paned with large thermal bridges to the outside. For the windows on the south facing façade (the offices), UT recommends at least screens or a reflective coating (tinting) added to the inside of the windows to control radiant solar gain in the summer.  The same recommendation is made for the west facing facade.  The windows on the north and east facade will not receive as much solar heat, but replacing the cracked panes is recommended.  Good double paned VINYL frame (reflective coatings on south and west) windows would be the best addition to the thermal envelope.  Weather-stripping all doors and replacing broken glass is a low cost first step and possibly comes with AE rebates.  Costs should be estimated and there are AE rebates for this.  Curtains are not effective to reduce heat gain.  The attic insulation level should be inspected (there is an AE rebate for this).

HVAC

No air leakage tests have been done in the sanctuary although it appears to be very leaky.  The capacity of the sanctuary is 883, though typically there are no more than 400 occupants.  Heat is by radiators, without individual forced air systems. There seems to be a system for recirculating air in the buildings, but it does not seem to be directly connected to a heat or cold source. This recirculation system appears to just move air about the building to distribute the heat from the different radiators.  Temperature monitoring in the sanctuary and in the Education Building can be performed in order to see how well the HVAC system is working and to get an idea of the number of air changes per hour.  Once that information is obtained, UT can determine how "leaky" the building is and make some recommendations for improvements.

For loud A/C on the 3rd floor, UT recommends replacing registers with proper high flow, directional registers (easiest), or reduce flow rate with dampers or fan speed.  This could be a full HVAC commission possibly requiring even reduced cold water feed, but air should not be too cold in the ducts, which can cause condensation.  There are many fan switches throughout the building for modulating air flow.  The thermostats control the chilled water flow, not the fans.  There should be quarterly inspection of air filters and replacement if needed (UUMC has regularly scheduled inspections by janitorial staff).

Chiller/Boiler

The chillers are located near the Fellowship Hall.  There are two chillers with three pumps that supply the whole facility.  It takes 1.5 hrs. to cool the sanctuary.  There is no cold water storage available.  Individual air handler units exist where AC is needed. These use chilled water and fans to produce cooling.  The chillers work in primary – secondary mode (second one only comes on when actual demand is higher than first can supply).  Each month, their roles are reversed to even out usage between the chillers.  Pumps are assigned as follows: pump 1 = 1st and 2nd floor; pump 2 = 3rd and 4th floor; pump 3 = sanctuary.  There are two boilers; one for the sanctuary and one for everywhere else.  Boilers come on when the outside air is less than 50 degrees F and the inside temperature is less than 65 degrees F.  The bathrooms do not have hot water; there is gas heat for hot water in kitchen.  Replacement of one or both compressors could be considered in the future, but only the one that is used more frequently.  Both are near their stated lifetime, but seem to be in good shape.  UUMC should make sure the coils are kept clean (watch for tree/leave debris) and they were clean when inspected.  Maintenance frequency appears to be OK.  The temperature of the liquid condensing should be 120°F.  If they are hotter, this is a sign of inefficiency.  In fact, one can tell by feel (touching with hand) whether the temperature is getting too high.  The coils should be shaded (as they are now) and not in direct sun.

Both chillers are the same model.  They appear to be tied to the same supply and return lines.  UT could collect data on the power consumed by each of the chillers to see if one is used more frequently than the other, and then estimate the current efficiency of the chillers as well as the anticipated efficiency improvement by making upgrades (either replacing the chiller entirely or getting a new compressor).  Using this information, UT can do a cost analysis for various scenarios, e.g., replace one, replace both, upgrade one, upgrade both, or do nothing.

The two Trane chiller units are 18 years old and have a 20+ year life.  It is important to be sure they are running efficiently making sure there is adequate air flow and checking the coils and fins to ensure they are clean (for good heat transfer).  A possible eventual upgrade in changing out the compressors in favor of scroll compressors was investigated.  The feedback from Trane is these new compressors run 30% more efficiently, under part-time usage scenarios.  Because the church only runs the units 50% of the time (or less), they probably have another 10+ years of life left in them.

Trane recommended an installation company in Austin that will provide a quote to determine what it would cost to change out compressors on both units.  The initial cost savings look attractive, with a savings of about $5500 per chiller, giving a payback time of about 11 to 12 years (new chiller cost=$40,000  + labor).  If one chiller fails in the near future, acquiring a new chiller will have some operating power cost savings to offset the capital cost.

Power Usage Monitoring

T.F. Edgar requested permission from Austin Energy to obtain data from the smart utility meter at UUMC, and AE has agreed to provide summary information (Excel) to UT, but they control access to the data.  The data tracks power usage at the church on a 15 minute interval basis.  Other monitoring equipment available at UT or Austin Energy could be employed to examine key components in the church energy system.  Observations on power consumption profiles (plots) were made: Average Saturday consumption is about equal to Sunday consumption.  The homeless program on Saturdays uses the Education Building for a half day, while on Sunday, both the sanctuary and Education Building are used.  Under the IHN program, families sometimes stay overnight.  In July, no early service was held on Sunday, so startup of A/C was delayed by one hour and there was lower usage.  Both lights and A/C are turned on at the same time.  UUMC generally needs one hour lead time to cool down the buildings.  Spikes in usage were due to chiller on-off duty cycle.  One chiller runs all of the time, while the second chiller is on-off based on demand.  The ramp down on Sunday can occur after 1pm - 2pm if there is a luncheon after church service.

Usage charts for the University United Methodist Church (UUMC):

Average Daily kW Profiles

Average Weekday, Saturday, Sunday kW Profiles

Monthly kW Use

Average Weekday, Hourly kW Profiles

Average Saturday, Hourly kW Profiles

Average Sunday, Hourly kW Profiles