Toyota Production System (TPS) & $1/Watt PV System Challenge

$1/Watt PV System – BoS /Installation Challenges for Ground Mounted Systems

The $1/watt White Paper from the U.S. Department of Energy was a great start to kickoff discussions and movements towards the goal of making solar power competitive without any incentives. To achieve this goal, the cost of an installed PV system would break down into the following components:

•    $.50/watt for Modules

•    $.40/watt for BoS/Installation

•    $.10/watt for Power Electronics

Module Prices and Power Electronics are Getting There

With new production capacities going online almost every week and new players consistently entering the global market, it seems that the question is not if, but when the module prices will hit the $.50/watt. Innovation, scale of production and fierce competition will lead the way to the defined goal, not only for the modules, but also for power electronics.

BoS/Installation

Currently, physical system costs, including labor, are accounting for about 75% of BoS costs for a ground-mounted installation. These costs are divided between structural components and the electrical system.

How can these costs be driven down to the $.40/watt goal? A 2010 Rocky Mountain Institute (RMI) workshop suggested the following steps:

•    Reduce forces at work – such as reduction of the wind load

•    Optimize structural form and materials

•    Design for low-cost installation

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Which Solar Ground-Mount Should You Use?

The many different types of mounts for solar arrays, be it fixed-, single-, or dual-axis trackers, can lead to considerable confusion when trying to decide how to mount your solar panels. However, there are several advantages and disadvantages to each type of mounting system depending on a variety of variables including climate, latitude, landscape, budget, and size of the solar array that you are hoping to build.

Fixed-axis systems are the most mechanically simple, and least expensive mounts for solar panels. They can be used on the roof or on the ground, and because of their mechanical simplicity, tend to have a longer lifespan than trackers. These mounts are also beneficial in less sunny climates, where extra expense of a solar tracker may not be worth the small increase in electrical output.

If you decide that you want a solar tracker, there are many options that you can choose from. Firstly, there are thermal (passive) and electrical (active) trackers. Thermal trackers use the heat from the sun, which heats a liquid inside of the solar panel, to rotate. These are beneficial because they have fewer mechanical parts, and are therefore less prone to failure. They are also less expensive. However they can be slow to react to solar motion. In addition, they can be imprecise in the winter because they rely on heat to rotate. Finally, there are electrical trackers, which are the most popular. They are very precise even in the winter, and can increase electrical output from 20-40% from fixed-axis mounts. However, they require a fair amount of maintenance and are more expensive than fixed-mount and thermal trackers.

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Foundations for Ground Mounted Solar Installations

Ground-mounted systems are probably the simplest way to install solar on a larger scale compared to other types of installations such as roofs or parking structures. These systems can be held down by a variety of foundations, including concrete footings, pile driven posts, piers, metal earth screws or with ballasted holding trays.

One size fits all ?

Foundation systems need to correspond to the existing site considerations and soil  static conditions according to engineering calculations and  building codes. The one size fits all approach will not lead to the most cost and resource efficient results. Here are some key factors that will help to determine the foundation type:

  • Tilt angle and tracking characteristics of the solar power system.
  • Local design wind speeds and snow loads (If applicable) where the solar power system is to be installed.
  • Support and racking configuration.
  • Overall solar module system size and weight.
  • Local design codes and project requirements.
  • Soil characteristics relative to friction, sliding, consolidation, slope stability, salinity, etc.
  • Brownfield or landfill

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Mounting Systems – the base of solar power

A recent survey performed by Photon USA Corp. reveals an increasing number of mounting system manufacturer in the U.S. market. This is not a surprise taking into account that the market has grown by 25 percent and more since 2010. Today installers can choose from no fewer than 262 products manufactured by 56 companies.

Keep it Simple 

The general perception is that mounting systems are cheap and simple and that prices always have to go down. The truth is that prices depend on the spot market for commodities like aluminum and steel and these markets have been very volatile for the last few years. Especially the last months have shown that prices tend to go up rather than down.

By focusing too much on material costs project developers have underestimated the impact of the labor factor in the overall costs of a mounting system. Some manufacturers have re conceptualized their systems to reduce the amount of material needed as well as the time to install the system.

Industry overview

In our upcoming posts we will discuss the advantages and disadvantages of steel versus aluminum, pile driving systems versus concrete foundations and who is offering what type of mounting system.