www.ResidentialSolar.companyOther solar products and services

Solar Water HeatersA solar water heater uses the radiant heat from the sun to heat water. A typical solar water

heater consists of a collector and tank. The collector is the part that absorbs the radiant heat and transfers it to the water. The water in a solar water heater the circulation can either be natural circulation (passive systems) or forced circulation (active systems).

The different types of solar water heaters based on collector types are:

Flat plate collector Evacuated Tube collector Heat pipe

Flat Plate CollectorsIn flat plate collectors the collector consists of a flat absorber plate which is black coated to

absorb solar radiation. This absorbed radiation is then transferred to the water through water channels attached to the back of the absorber plate. The entire collector is enclosed in an insulated box with a double glazed glass top. The water can be heated to temperatures of 50 to 60°C. The thermal efficiency of a flat plate collector is 40 to 50%.

Evacuated Tube CollectorsAn evacuated tube collector consists of an annular absorber plated enclosed by an

evacuated tube. The irradiative heat from the sun is collected by the collector and transferred to the water. The main advantage of using an evacuated tube collector is that it reduces the convective heat losses to the atmosphere. The water can be heated to 60 to 80°C. The thermal efficiency of an evacuated tube collector is about 60%.

Heat Pipe Heat pipe is similar to an evacuated tube collector but here a low boiling point liquid (e.g.:

ammonia) is used to heat water indirectly. The heat pipe may or may not be enclosed by an evacuated tube. The main advantage is that it can be used in places where temperature drop below 0°C during the night as there is no problem of freezing in collector. The water can be heated to 50 to70°C.

Sizing Of Solar Water HeaterThe quantity of hot water required is the main parameter to size the solar water heating

system. A rule of the thumb is for a 100 L solar water heater to heat water from 30°C to 70°C requires 2 m2 of collector space at SOTC (Standard operating test condition).

Solar PhotovoltaicSolar photovoltaic deals with the conversion of light directly into electricity and is a type of

direct energy conversion system. A solar photovoltaic system can be classified into the following types:

Grid connected systems Stand-alone systems Hybrid systems

Grid Connected SystemsA grid connected photovoltaic system consists of the Photovoltaic panels, power

conditioning unit (PCU), inverter and transformers. The PV panels convert the light into non-stabilised DC electric power. This non-stabilised DC voltage is stabilised by PCU. The conditioned DC voltage is converted to AC power by the inverter. The AC voltage is stepped up to 11kV or 33kV and is then fed into the grid by the transformers.

Stand Alone SystemsA stand-alone photovoltaic system consists of photovoltaic panels, power conditioning unit

(PCU), an inverter and may or may not have a battery bank. This type of system only produces power which powers a local load and excess power to charge batteries or power an auxiliary load.

Hybrid SystemsA hybrid system is basically a combination of a grid connected and stand-alone system. A

hybrid system may also have other power producing systems such as diesel generators connected to it. The main advantage of a hybrid system is that it can provide power even when one of the power sources fails to produce power.

Sizing Of Solar Photovoltaic SystemSizing of any solar photovoltaic system depends upon the load it has to support. Let us for

simplicity assume designing a photovoltaic system to power 2 fans and 2 tube lights which operate for 8 hours each.

Load = ( 2* 60 * 8 )fans + (2*40*8) tube lights = 1600 Wh

Power required = 1.2*[(2*60)fans + (2*40)tube lights] = 200 W [ 20% extra for design]

For such a system a single 250 Wp panel is sufficient

Inverter capacity = power required + 15% = 230 VA

Hence a 250 VA inverter will also be sufficient

For battery backup with 1 day autonomy,

Battery capacity = (load * days of autonomy) / (system voltage * DOD)

Battery capacity = (1600 * 1) / 12 *0.8 = 166.67 Ah

So a 150 Ah will be suitable as getting an higher rated battery say 200Ah will be costly.

Information on other solar products and services can be found here.