raw · articles · ingested 2026-09-19
Oregon Institute of Technology Geothermal System — the 1980–1998 LiBr Absorption Chiller (Geo-Heat Center Bulletins 1999 & 2010)
Source: https://www.osti.gov/etdeweb/servlets/purl/895238
Provenance: Two Geo-Heat Center Bulletin articles by the campus’s own geothermal engineers (Boyd 1999; Lund & Boyd 2010), DOE-funded. Primary operating history of the first US geothermal absorption chiller. Retrieved via research agent; PDFs extracted locally.
The campus resource
Three wells 1,300–1,800 ft (400–550 m) deep, 192 °F (89 °C), total 980 gpm (62 L/s); heats ~11 buildings / 600,000 ft² (2010); saved 11,000 bbl oil/yr ($225,000/yr in 1999).
The chiller
| Parameter | Value |
|---|---|
| Type | LiBr/water single-effect absorption, geothermal water directly in the generator tubes (90-10 cupro-nickel) |
| Nominal capacity | 312 tons (1,095 kW) |
| Installed | 1980, recorded cost $171,300 |
| Served | Base cooling for 5 buildings, 277,300 ft² (25,800 m²); chilled water 44 °F (7 °C); pre-existing electric centrifugal for peaking |
| Rated drive temperature | 240 °F (116 °C) for 100% output |
| Actual drive | 89 °C → 150 tons (526 kW), ~48% of nameplate |
| Heat-side flow | 685 gpm (37.8 L/s) at only 20 °F (11 °C) ΔT → ~4.6 gpm per delivered ton (2010 article rounds to 600 gpm / 38 L/s) |
| Retired | Summer 1998 (2010 article) / 1999 (1999 article says “this summer”), replaced by an electric centrifugal chiller |
Why it was retired
- “Due to the low efficiency and high water usage, the absorption chiller will be replaced this summer with a centrifugal water chiller.” (1999)
- “Unfortunately, the unit at that time required 240˚F (116˚C) geothermal water to operate at 100% efficiency, thus the machine only produced half of the normal output. For this reason, and the required high geothermal flows (600 gpm – 38 L/s), high discharge temperature and corrosion of the copper pipes in the generator section, the unit was replaced with an electric chiller in 1998 (Lienau, 1996).” (2010)
- No generator tube failures in 18 years, but corrosion was cited among the reasons for retirement. The high discharge temperature (only 11 °C extracted) also meant most of the pumped heat went back to disposal unused.
Campus-wide materials lessons (applicable to any direct-use chiller)
- H₂S and ammonia in the geothermal water destroyed 50/50 tin-lead and 1% silver solder, thinned copper tubing, and failed brass and stainless crimped valve plugs → the campus moved to plate heat exchangers isolating the geothermal loop.
- Direct-buried steel pipe corroded → 1980 utility tunnel at ~$160/ft ($525/m).
2010 US direct-use context (same issue)
Cooling and snow melting are the two smallest US geothermal direct-use categories. The Chena ammonia unit “keeps a 1,000 tonnes of ice frozen even though it reaches 32 °C outside.”
Key quote
“It has a nominal 312 ton (1095 kW) capacity; but due to the low temperature of the water entering the system (192oF/89oC), it only produces 150 tons (526 kW) of cooling. The chiller requires 685 gpm (37.8 L/s) of geothermal fluid and only takes a 20oF (11oC) delta T out of the water.”
Relevance to the cooling wiki
The canonical cautionary tale for geothermal-driven LiBr cooling: an 89 °C resource that looks adequate on paper delivered half the nameplate, needed three times the heat-side flow, corroded, and lost to an electric chiller once electricity was cheaper than pumping 38 L/s of hot water. Vintage matters — the 1980 machine was rated at 116 °C; modern low-temperature LiBr units (Yazaki class, 70–95 °C) are rated differently — but the flow-per-ton and materials lessons stand.