Archive for Category Solar Photovoltaic Power Plant

1. Inverters and BOS in Roof Top PV Systems

BOS, Balance of Systems and Inverters are integral parts of any Solar Power Generating unit. It is imperative that specified BOS and inverters are used for any given configuration of a solar power system for optimal energy efficiency. BOS includes the wires connectors, AJB’s etc. For Energy Efficiency, it is important to use the wires with correct thickness to avoid heat loss and voltage drop. Ohm’s law ( V=IR ) quantifies the voltage drop as a function of current and resistance. The figure below broadly indicates the wire thickness v/s current function to minimize the voltage drop.

The MPPT Charge Controller

MPPT (Maximum Power Point Tracking) Charge Controller tries keeping the panel at its maximum voltage and simultaneously produces the voltage required by the battery. A basic charge controller simply prevents damage of batteries by over-charging, by effectively cutting off the current from the solar panels (or by reducing it to a pulse) when the battery voltage reaches a certain level. On the other hand, a Maximum Power Point Tracker (MPPT) controller performs an extra function to improve your system efficiency.

What does the MPPT Controller Do ?

Besides performing the function of a basic controller, an MPPT controller also includes a DC to DC voltage converter, converting the voltage of the panels to that required by the batteries, with very little loss of power. In other words, it attempts to keep the panel voltage near its Maximum Power Point, while supplying the varying voltage requirements of the battery. Thus, it essentially decouples the panel and battery voltages so that there can be a 24 volt system on one side of the MPPT charge controller and panels wired in series to produce 48 volts on the other. Thus, offering the ability to provide some charging current even in dull conditions when a simple controller would not help much.

Inverter Efficiency

Solar PV system produces DC current, which is converted to AC using an inverter. Although inverters come with wide ranging efficiencies but typically affordable solar inverters are between 80% to 90% efficient.

Battery Efficiency

Batteries are needed for charge storage. Lead acid batteries are most commonly used.

Since lead acid batteries are usually charged at the float voltage of about 13.5 V and the discharge voltage is about 12 V, the voltage efficiency is about 0.88. In average the coulomb efficiency is about 0.92. Hence, the net energy efficiency is around 0.80

A lead-acid battery has an efficiency of only 75-85% (this includes both the charging loss and the discharging loss). From zero State of Charge (SOC) to 85% SOC the average overall battery charging efficiency is 91%- the balance is losses during discharge. The energy lost appears as heat which warms the battery. It can be minimized by keeping the charge and discharge rates low. It helps keep the battery cool and improves its life.

2. Domestic Solar Power and Diesel Generator Electricity Cost Evaluation

Domestic Solar Power generation using BIPV ( Building Integrated Photo Voltaic) Products, e.g. Roof top Solar systems etc. have slowly become mainstream products, with falling costs of PV panels and ever increasing costs of fossil fuels. Energy is an essential requirement for survival. May it be heat, light or any form of mechanics- everything needs energy. The remote villages in India are still deprived of electrical supply from the conventional grid source. The Diesel Generator (DG) sets are being used for power but its operation is limited due to high cost of fuel and high maintenance.

Silent Features

  • The projections are on CURRENT PRICE TRENDS. Diesel prices are BOUND TO RISE and PV PANEL PRICES predicted to fall IN FUTURE.
  • Even if you include the interest cost in the first 5 years, the DOMESTIC SOLAR POWER GENERATOR is way cheaper than the Gen-set option.
  • Cost of production of electricity by Domestic Solar Power Generator, is currently at par with the grid tariff . It is bound to fall in future, thereby making it EVEN CHEAPER THAN THE GRID IN FUTURE.