Solar Energy Basics

How Does Solar Energy Work?

Solar Photovoltaic (PV) cells convert the sunlight to direct current (DC) electricity. The inverter converts DC into alternating current (AC) electricity which is then used onsite, sold back to the utility company, or stored in batteries.

A Solar Module is made up of 60 to 72 solar cells. Each solar module is about 20 square feet (5.5′ x 3.33′ for 60 Cell Modules or 6.5′ x 3.33′ for 72 Cell Modules) and weights approximately 50 pounds.

The Inverter is considered the “brains” of the system. There are three types of inverters: 1) String Inverter 2) Microinverter 3) DC Optimizer Inverter.

how_solar_power_system_works

Types of Installation

  • Roof (flush) Mount
  • Roof (flat) Mount
  • Ground Mount
  • Pole Mount
  • Grid Tied
  • Battery Backup
  • Off Grid

Net Metering vs Batteries

Net Metering: a system in which solar panels or other renewable energy generators are connected to a public-utility power grid and surplus power is transferred onto the grid, allowing customers to offset the cost of power drawn from the utility. Without battery backup, the solar system shuts down in the event of a power outage

Design Considerations

  • Roof Age & Condition: we like to see roofs with at least 15 years of service life remaining.
  • Roof Slope: 30-35 degree slope is ideal, but a larger or smaller angle works just fine too.
  • Roof Orientation: due south is ideal. Any orientation will work, but the further north the solar array faces, the lower the solar production.
  • Types of Solar Modules: we like to use crystalline type modules consisting of 60 or 72 cells.
  • Types of Inverters: there are a handful of different inverters that we prefer to use. We’ve installed String Inverters, DC Optimized Inverters, and Microinverters. All have slightly different functions, different price points, advantages and disadvantages – but ultimately, they all convert sunlight into electricity.
  • Types of Racking:
    • Roof Mounted
      • Sloped Roof: The most popular installation is a roof mounted solar array. On houses and sloped roofs, we install a flush mounted racking system, so the solar modules are flush or parallel with the roof surface.
      • Flat Roof: On flat roofs, we utilize a ballasted racking system. Ballasted racking systems are nice because there are very few (if any) roof penetrations.
    • Ground Mounted
      • These are ideal when roof space is limited or shaded and ground space is abundant. While in roof mounted systems, the roof acts as the superstructure, ground mounted systems are typically more expensive because we have to build the superstructure.

Tools Used

Although we use an array of tools to design and install a solar system, here are a few that even home owners like to play around with:

  • Our favorite tool to evaluate a home or building for solar energy is Google Earth. It’s a free satellite imagery program that allows us to not only view the property, but to measure it with incredible accuracy. In most cases, we can even stroll back in history to see different seasons and how they might affect shading – and ultimately, solar production.

    Google Earth Satellite Photo from one of our first solar installs.
    Google Earth Satellite Photo from one of our first solar installs.
  • We currently use AutoCAD to develop the engineered drawings for permitting, utility interconnection, and installation.

    AutoCad is used to create design documents.
    AutoCad is used to create design documents.
  • PV Watts Production Calculator. This solar production calculator utilizes 30+ years of historical weather data as well as location, roof slope, roof orientation, installation type, and other important inputs to estimate the annual solar production of a specific solar installation. pvwatts