Design Outcome
Designing a PV array’s energy use depends on many factors,
including weather and location.
Cable, conversion, and mismatch losses make up the
value of V. (Others, such as temperature and shading, will be
necessary for better accuracy.)
Summarization of Calculation Methods for Designing
a PV Array
There are two primary ways of designing the array:
Set a budget, and design a system that meets that budget.
Design a system that meets the expected needs with the ability to expand.
Set a Budget and Design a System That Meets That Budget
The first action is to make the system owners understand that they will not neces-
sarily have all the energy they want or need when they want it. The owners may
have to change their energy usage patterns or do without electricity at some times
of the day or year. This may require a phased design approach. The phased design
approach adds to the system as the customer’s needs or budget, or both, expand.
Every designer and installer must have the phased design approach conversation
with the customer; otherwise, the customer may not be given an optimal system.
Design a System That Meets the Expected Needs with the Ability to Expand
This approach will give the customer the capability to expand to meet his or her
future demands. With this method, the designer will work from the load back-
ward. The quality of design and components combined with the installation pro-
cess will determine the quality and performance of the system when completed
and operating. Such an approach involves:
Establishing the load on a monthly basis year-round and taking a close look
at matching load to what will be determined below.
Determining all of the system losses within a range based on product types
and proper sizing. Initially, this will be very time consuming; however, with
experience, you will be able to do this quickly.
Deciding whether there should be a battery bank or other backup system.
Calculating the battery bank size and autonomy. For cold climates, it will
be based on the winter load and array size. For hot climates with air
conditioning, it will require careful determination of the summer loads.
Sizing the array on the basis of a thorough understanding of the local
environment and site conditions.
In previous chapters and books, we covered all the factors involved in doing
this. Keep in mind the fact that you will have the highest performance by using the
NOTE
Remember that the batteries will not
hold all of the PV-generated energy in
most systems without a large battery
storage system. Adjustments between
PV array, battery, and backup power
will need to be made to maximize
the system’s production in order to
minimize waste.
CHAPTER 6 Standalone PV Systems 131
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