Page 143 - Solar Power in Building Design The Engineer's Complete Design Resource

SOLAR POWER DESIGN 113

■ PV module area: 14 ft 2
■ Approximate available unshaded platform space: 7500 ft 2
■ Total number of PV modules to be installed: 530 units
■ Total PTC output watts: 530 × 158.3 = 83,899 W
■ Inverter unit capacity chosen: 100 kilowatts (kW)
■ Inverter efficiency: 94.5%
■ Total eligible rebate watts: 83,899 × 94.5% = 79,285 W
■ Adjusted incentive rebate per watt: $2.50
■ Total rebate eligibility: 79,285 × $2.50 = $198,212.50

Note that the maximum allowable rentable solar energy is regulated and capped by
various rebate administrative agencies. For instance, Nevada Power caps the small
commercial rebate to 30 kW per user meter, whereas the Los Angeles Department of
Water and Power caps it to a maximum of 300 kW per user per meter and Southern
California Gas and Southern California Edison limit the cap to 1000 kW per user
address or meter per year.
It is suggested that the solar power design engineers before commencing their
design should familiarize themselves with the specific requirements of energy service
providers.
Additional documents that must be provided with the rebate application form are as
follows:

■ Electric power system single-line diagrams that show solar power PV arrays, dc
combiner boxes, inverters, ac combiner boxes, conduit sizes, feeder cable sizes
and associated voltage drops, the solar power fused service disconnect switch,
the solar power meter, and the main service switchgear solar disconnect circuit
breaker.
■ Total building or project electrical demand load calculations (TBDL)
■ Calculated percentage ratio of the total eligible rebate watts: (TERW/TBDL) × 100.
This figure is required to confirm that the overall capacity of the solar power cogen-
eration does not exceed 125 percent of the total project or building electrical
demand load.
In order to protect the client and avoid design error and omission liabilities, it is
suggested that all documents and calculations be prepared by an experienced, quali-
fied, registered electrical engineer.
Example of a solar power design Upon the approval and confirmation of the
rebate by the energy service provider, the solar power engineer must undertake a com-
prehensive study of the entire solar power system and provide the following design
documentation and paperwork to the agency for final incentive rebate approval. Note
that times for submitting the required documents outlined here are mandatory, and
they must be completed within a specified period of limited time.
To start the final solar power design, the electrical or solar power designer must
conduct a thorough solar shading evaluation. If the solar platform is surrounded by