I have a few questions regarding modeling of a LEED CS building using option #2 from the Treatment of District or Campus Thermal Energy in LEED guide. This is in regard to a DES that provides chilled water only.
We have monitored the DES cooling plant for a complete year and have determined the average efficiency of the plant. A thermal energy storage tank is to be added to the cooling plant to shift the energy use to the off peak time period of the energy tariff.
Under Option#2 of the LEED guide in section 2.4.2.2-4 would it be allowed to do the following:
1. Use the monitored averaged efficiency from the DES equipment in the proposed case energy model and
2. Model a thermal energy storage tank in the proposed case energy model sized to shift the cooling to the off peak time period and
3. Model the proposed case cooling equipment (chiller, pumps, cooling tower) as the same type as those in the DES with the chiller sized at 1.15 times the peak building load and
4. Separately meter the building and plant (in both proposed and baseline) with the associated building and DES energy tariffs (time of use based) tied to those meters?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 17, 2013 - 1:27 pm
1-yes
2-yes
3-yes except you do not add the 15% oversizing.
4-I am not sure why you would need to create separate meters for the building and plant. The plant, including the thermal energy storage, is a virtual on-site plant under Option 2. Maybe I am not interpreting your last issue correctly.
Matt Humphreys
September 17, 2013 - 2:46 pm
Introduction of the separate meters allows the use of one utility tariff for the building and a separate tariff for the plant which is based on time of use. The plants utility tariff favors shifting of the energy used for cooling to the off peak demand window (which is what the TES is designed to do). This is an option under 2.4.2.2-(b). However the difference here is we don't have monitored average plant efficiencies for each utility time block for the plant with the TES because the TES is new to the existing plant. Therefore we propose to use the average plant efficiency (monitored from an entire year without TES) and add a virtual TES to the model because the simulation program is capable of modeling a TES.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 17, 2013 - 3:24 pm
Now it makes sense, thanks. If the tariffs are different then model it as close to the actual situation as possible. Make sure to use the identical rates in the baseline.