We would like to confirm the applicability of a District Lake Source Cooling (LSC) operation as an eligible on-site renewable energy source for LEED NC 2009 and LEED v4 BD+C. This innovative Lake Source Cooling facility, which has been in operation since 2000, uses the deep cold waters of a large lake as a non-contact renewable cooling source for a campus chilled water system. At a depth of ~250ft the bottom of the lake maintains a steady year-round temperature of 39-41 F. The only energy used in the system is pumping energy and the system has demonstrated an 86% reduction in energy use over conventional water cooled chiller. Extensive environmental impact studies were carried out prior to and after operation and all have concluded that adverse environmental impacts have been minimized or avoided. It does not use any vapor compression cycle and no water is wasted.
The LEED 2009 Reference Guide states "geothermal energy systems using deep-earth water or steam sources (but not vapor compression systems for heat transfer) may be eligible for this credit." The project team proposes to account for the renewable energy credit by calculating savings between the proposed case model with LSC system and a proposed case model with conventional refrigeration system that complies with the ASHRAE 90.1 code requirements.
The applicant is requesting whether deep-water Lake Source Cooling that replaces the refrigeration cycle for the campus central plant system may be used to claim credit for on-site renewable energy for the project under EA Credit 2: Renewable Energy Generation. The proposed approach is not acceptable since the lake source cooling does not qualify as a geothermal energy source using deep water or steam sources. Furthermore, the resource would be depleted and would have a negative environmental impact if the cooling capacity were increased exponentially (i.e. the resource provides increasingly less environmental benefit for other/subsequent projects beyond this one); therefore it is not considered on-site renewable energy.
It is noted that the proposed approach is an extremely efficient form of cooling, and while no credit is allowed as an on-site renewable source, significant credit would be achieved for EA Credit 1: Optimize Energy Performance using the ASHRAE 90.1 Appendix G modeling processes.