Reliability
PV panels normally provide a 25 year life time and manufacturer's warranty, while PV inverters have only recently extended their warranty from 5 to 10 years. Total system costs need to consider both original and replacement costs for the inverter system over the 25 life time of the PV system. As result the inverter cost and reliability are a major factor in cost effectiveness of the PV system. The importance of this factor will grow as the cost of PV modules decrease sharply over the next few years. - Sandia Inverter Reliability 35KB pdf
Several key issues reduce the lifetime of inverters. The most important are:
- operating temperature of the electronics, and
- electrical transient stresses.
The operating temperature issue is common to all electronics, but the electrical transient stresses primarily effect high power systems.
- The operating temperature of the electronics is determined by ambient temperature, the amount of waste heat generated (heat dissipation), and the ability of the system to transfer the waste heat out the system. The most important design issue is to provide high efficiency of operation to reduce heat dissipation. If the heat dissipation is low enough, cooling fans can also be eliminated. This reduces maintenance and potentially improves reliability, as forced air systems have screens that need to be periodically cleaned.
- Power electronics have an additional critical issue with electrical transient stresses. The large electrolytic capacitors used in these products are generally considered the most likely component to fail. Reducing the electrical stress on the electrolytic capacitor components will increase operating life time of the inverter and the entire PV system
The Total Energy Company converter / inverter system's high efficiency reduces heat dissipation. It is the first fully soft-switching inverter system where the switching occurs only at zero voltage and zero current times. This improves switching efficiency, but also minimizes electrical transients that stress sensitive electrolytic capacitors and extend operating life.
Weight
PV inverter and power conditioning systems are expensive components to install. A major reason for this is the high weight of these products. Commercially available 5KW inverters systems weigh 100 to 150 lbs. These units require expensive freight shipping and several qualified individuals to install. Total Energy Company' 5KW inverter weighs less than 25 lbs. This allows the unit to use lower cost shipping and installation by a single individual.
This dramatic weight reduction was accomplished by eliminating heavy transformers and replacing them with solid state electronics. Total Energy Company plans to develop higher power systems where it expects an even greater improvement in the power/weight ratio compared to traditional inverter systems.
Cost
Current PV inverter products have high costs due to expensive components and high engineering costs/unit. The component costs of the Total Energy Company inverter solution is lower than existing units of the same power level since the most expensive components (large transformers and capacitors) are eliminated. The cost of these large transformers and capacitors is driven by commodity materials costs such as copper and iron. The Total Energy Company component cost is driven primarily by commercial semiconductor components whose pricing decreases over volume and time.
The cost of current PV inverters is further limited by the high development and engineering cost per model and the large number of models required by the industry. In additional to supporting a wide range of power levels, separate inverter designs are required for 1) grid-tied, 2) grid-tied battery backup, and 3) standalone applications. The Total Energy Company solution supports all these applications with better cost, flexibility and efficiency metrics than existing products. This enables a single hardware design to address a much broader market area. Furthermore the Total Energy Company product can be customized with software enabling a build-to-order manufacturing model with standardized hardware components and final stage software customization.
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