Building projects may incorporate other on-site electricity generation equipment, such as cogeneration plants or fuel cells that make electricity and produce heat. Projects may also include wind turbines. These systems may be modeled in various ways and the building descriptors described below should be considered an example of one set. In all cases, the baseline building will be modeled without on-site generation equipment. If there is no thermal link between the power generation equipment and building equipment (such as heat recovery from CHP), on-site power generation can be modeled in a separate process, otherwise, it needs to be linked to the building simulation.
Building projects may incorporate on-site electricity generation equipment, such as photovoltaics (PV) and wind turbines or combined heat and power or fuel cells that make electricity and produce heat. These systems may be modeled in various ways. Descriptors have been added below for PV, combined heat and power cogeneration and wind turbines. Fuel cells are not addressed by this manual currently. In all cases, the baseline building will be modeled without heat recovery from on-site generation equipment. If there is no thermal link between the power generation equipment and building equipment (such as heat recovery from combined heat and power [CHP]), on-site power generation can be modeled in a separate process; otherwise, it needs to be linked to the building simulation.
On-site renewable energy shall be subtracted from the proposed design energy consumption prior to calculating the proposed building performance, additional details are provided in Section 1.3. On-site renewable energy generated by systems included on the building permit that is used by the building is considered free and shall not be included in the proposed design energy cost for renewable energy contributions up to 5% of the baseline building performance. When renewable energy contribution of the on-site renewable energy generation system exceeds 5% of the BBP, the PCI will be calculated as explain in Section 1.3 of this manual.
Building projects may incorporate on-site electricity generation equipment, such as photovoltaics (PV) and wind turbines or combined heat and power or fuel cells that make electricity and produce heat. These systems may be modeled in various ways. Descriptors have been added below for PV, combined heat and power cogeneration and wind turbines. Fuel cells are not addressed by this manual currently. In all cases, the baseline building will be modeled without heat recovery from on-site generation equipment. If there is no thermal link between the power generation equipment and building equipment (such as heat recovery from combined heat and power [CHP]), on-site power generation can be modeled in a separate process; otherwise, it needs to be linked to the building simulation.
On-site renewable energy shall be subtracted from the proposed design energy consumption prior to calculating the proposed building performance, additional details are provided in Section 1.3. On-site renewable energy generated by systems included on the building permit that is used by the building is considered free and shall not be included in the proposed design energy cost for renewable energy contributions up to 5% of the baseline building performance. When renewable energy contribution of the on-site renewable energy generation system exceeds 5% of the BBP, the PCI will be calculated as explain in Section 1.3 of this manual.
The PCIt (performance cost index target) equation in Standard 90.1-2022 Section 4.2.1.1 includes a term to account for proposed building performance excluding any renewable energy systems in the proposed design and including an on-site renewable energy system that meets but does not exceed the requirements of Section 10.5.1.1 (note there are no renewable energy requirements for alterations) modeled following the requirements for a budget building design in Table 12.5.1, row 15 (PBPpre). Recall from Section 1.3, for a project following 90.1 2022 Appendix G to be considered minimally compliant with 90.1 2022 the PCI performance cost index (PCI) needs to be less than or equal to the PCIt.
The modeling requirements in Table 12.5.1, row 15 Budget Building Design column prescribe the following:
- Where a system providing on-site renewable energy is specified in the proposed design, the same system shall be modeled for the purpose of establishing PBPpre (proposed building performance including only prescriptive renewable energy requirements), except the modeled rated capacity shall meet the requirements of Section 10.5.1.1. Where more than one type of on-site renewable energy system is specified in the proposed design, the total capacities shall be allocated in the same proportion as in the proposed design.
- Where no system exists or is specified to provide on-site renewable energy in the proposed design, on-site renewable energy shall be modeled as an unshaded photovoltaic system with the following physical characteristics for the purpose of establishing PBPpre (proposed building performance including only prescriptive renewable energy requirements):
- Size: Rated capacity per Section 10.5.1.1
- Module Type: Crystalline silicon panel with a glass cover, 19.1% nominal efficiency and temperature coefficient of –0.19%/°F; performance shall be based on a reference temperature of 77°F and irradiance of 317 Btu/ft2h.
- Array Type: Rack-mounted array with installed nominal operating cell temperature (INOCT) of 103°F
- Total system losses (DC output to AC output): 11.3%
- Tilt: 0-degrees (mounted horizontally)
- Azimuth:180 degrees
If the on-site renewable energy system cannot be modeled in the simulation program, Section G2.5 shall be used.
G3.3 Minor Alterations
Energy generated by existing system capacity shall be subtracted from the baseline design energy consumption prior to calculating the building performance. Additional capacity and/or a new system included in the scope of the alteration is not required to be subtracted from baseline design energy consumption.