Square Feet: 138,000 | 62%+ natural gas savings.
Energy Resources Group (ERG) evaluated Eden Theological Seminary’s aging central boiler plant and recommended converting the system from steam to hot water, then worked as the project manager and commissioned the replacement equipment.
Project description
In March 2018, David Greenhaw, the president of Eden Theological Seminary, requested that ERG assist with evaluating a steam boiler plant on the campus located at 475 E Lockwood Ave., in Webster Groves, MO. The central plant was originally constructed in the 1920s and provides heat for 70% of the campus. Eden’s campus includes academic buildings which operate during the days and evenings, and residence halls, which operate 24/7. These buildings serve approximately 200 students and staff. The existing equipment was 30+ years old. ERG estimated that the existing steam boiler system had a peak efficiency of 64%. Building benchmarking showed the building used 154,000 Therms of natural gas each year at a cost of $105,000. Combined with electrical use, the buildings on the steam loop had an Energy Usage Intensity of 155 kBtu/sf/year.
Annual repair expenses for the system had been increasing, and Eden was facing a repair expense of $150,000. This repair expense precipitated the investigation into replacement.
Recommendations
ERG investigated both natural gas and ground-source heat pump options and recommended replacing the single steam boiler with a high-efficiency natural gas hot-water system. These boilers have a 96% peak efficiency. Additionally, ERG recommended replacing the single piece of equipment with two smaller boilers. This would improve turndown, meaning that on milder days, which make up much of the heating season, only one boiler would be needed to meet the heating load, and it would be able to do so more efficiently; further increasing the energy and cost savings. With the old system, the steam boiler efficiency would decrease on milder days.
ERG estimated the high-efficiency replacement would cost $320,000 beyond what it would take to repair the old boiler and steam loop system, and that it would yield an energy savings of 55% ($54,500/year). In addition, ERG recommended that Eden pay for this project through an energy loan program from Missouri’s Department of Natural Resources. Eden moved forward on these suggestion on a tight time-table with the installation in the summer of 2018.
The scope of the project included:
- Replacing the boilers,
- Replacing the main condensate return,
- Replacing a tertiary pump,
- Removing building-level heat exchangers and traps from radiators,
- Repairing some piping leaks,
- Asbestos abatement,
- Addition of modern controls, and
- Management of the State Energy Loan Program and Utility Rebates.
Savings Analysis
The temperature vs. usage chart shown above correlates the gas usage data with outdoor air temperature. It shows data over the two years before changing from steam to high-efficiency hot water (the profile from May 2016 to February 2018 – red regression lines with circles and diamonds), along with the usage over the three years after the upgrade (October 2018 to November 2021 – green lines with squares and triangles).
Results
Upgrading the central boiler plant has reduced natural gas use 95,900 Therms (62%), which saves $66,300 and 580 tons of CO2 annually.
The cost differential that Eden faced, between repairs to the old steam system ($150,000) and the installation of a technically superior new system ($625,000), and with securing a Spire Energy Rebate ($66,000) was $409,000.
Enhancing Eden’s infrastructure has yielded a 6.2-year payback – a guaranteed 16% ROI. The annual energy savings effectively increase the endowment $886,000 at a 7% yield on a 20-year basis after project costs have been recouped.
