What is Solar Energy and What can we do with the power?
Well, before you ask that question, you really need to know the answer to this one:
What sort of power is it?
In case you didn’t know, solar panels don’t generate what we call "mains electricity”. Mains is 230 Volts AC (117 Volts in the USA), while solar panels generate about 12 Volts DC.
AC/DC – that’s a heavy metal band isn’t it?
Er, yes, but they’re not the same without Bon Scott are they? AC stands for Alternating Current and DC stands for Direct Current. The important differences are that the voltage of an AC source can be changed by using a transformer, whilst DC can’t. On the other hand DC can charge a battery whilst AC can’t. That’s why mains is always AC and car electrical systems are always DC.
Does that mean I can’t make solar power into mains with a transformer?
Correct, you need a device called an “inverter”. But you can charge a battery.
But I’m on the mains. Can’t I have solar power then?
Of course you can, don’t worry. You can connect solar panels to the mains using a “synchronous inverter”, and sell the extra power to the electricity company. The government may even give you a grant for doing it.
What’s a synchronous inverter?
It’s an electronic device that turns DC into AC and matches it to the incoming mains. Then, when there is extra power, it turns your meterbackwards.
I’ll have one, where do I get it?
Renewable Energy Solutions can be found here
So what if I’m not on the mains?
You might not live in the middle of nowhere but that still doesn’t mean you can get the mains. You might need power for a caravan or boat, or a holiday home overseas. Maybe your garage is the other side of the main road and you can’t bury a cable. The questions are the same.
What if it’s not sunny?
I reckon you know the answer by now. Charge a battery, that’s what.
Then, when the sun’s not shining or you need more power than the solar panels are producing it can come from the battery. If you do it right, during the day the battery will charge up again.
But I want mains, not battery power, don’t I?
I don’t know, do you? You can get a lot of 12 Volt appliances now, so
you might not need mains. Truck accessory people and the like sell them.
Have a look at my recommended suppliers for links. If you really do need 230 Volts AC you can use an “inverter”.
That’s the thing that sells electricity isn’t it?
That’s a synchronous inverter, this is a bit different. Instead of being connected to the solar panels, a stand-alone inverter is connected to the battery. It does the same sort of thing except it generates its own “mains” power. Solar power answers has a page all about inverters.
So, a solar panel, a car battery and one of these inverter things then?
If you like, but it won’t work very well or for very long. You see, there
probably won’t be the right amount of power, and the battery won’t last very long.
To understand more, take a look at our renewable energy solutions here and discover more answers to What is Solar Energy.
Tuesday, 28 August 2007
What is Solar Energy
Introduction to What is Solar Energy
Energy from the sun has been harnessed for thousands of years.
We use this energy in three main ways and when talking about
solar energy it is important to distinguish between these three
types:
• Passive heat: This is the heat that we receive from the sun
naturally. This can be taken into account in the design of
buildings so that less additional heating is required.
• Solar thermal: Where we use the sun's heat to provide
hot water for homes or swimming pools. We cover this
topic in another fact sheet: solar water heating.
• Photovoltaics (PV): Uses energy from the sun to create
electricity to run appliances and lighting. PV requires only
daylight - not direct sunlight - to generate electricity.
How PV technology works
Photovoltaic systems use cells to convert solar radiation into
electricity. The PV cell consists of one or two layers of a
semiconducting material, usually silicon. When light shines
on the cell it creates an electric field across the layers,
causingelectricity to flow.
The greater the intensity of the light, the greater the flow of electricity.
The three main types of solar cells are:
• Monocrystalline: made from thin slices cut from a single
crystal of silicon. This has a typical efficiency of 15 per cent.
• Polycrystalline: made from thin slices cut from a block of
silicon crystals. This has a typical efficiency of around 12 per cent.
• Thin Film: made from a very thin layer of semiconductor
atoms deposited on a glass or metal base. This has a
typical efficiency of 7 per cent.
Individual PV cells are connected together to form a module.
Modules are then linked and sized to meet a particular load
(need). The result is a PV array which supplies power to the
building it is fitted on. If the building has mains electricity, any
excess electricity can be exported to the national grid.
Alternatively, when demand is high, extra electricity can be
purchased from the national grid through the utility
companies. Where there is no mains supply, PV arrays can be
used to charge batteries.
PV arrays now come in a variety of shapes and colours,
ranging from grey 'solar tiles' that look like roof tiles, to
panels and transparent cells that you can use on
conservatories and glass to provide shading as well as
generating electricity.
Applications
There are many applications for PV, ranging from calculators,
solar torches and battery chargers to integrated systems for
homes, offices, factories and public buildings. You can use
PV systems for a building with a roof or wall that faces
within 90 degrees of south, as long as no other buildings or
large trees overshadow it. If your roof surface is in shadow
for parts of the day, the output of the system decreases.
Another consideration is that your roof must also be strong
enough to hold the significant weight of the panels,
especially if they are going to be placed on top of existing tiles.
Domestic installations
The size of a PV array required to provide electricity for a typical
home varies, depending on a number of issues; how much
power you need, the type of cell used, roof space available and
budget. Typical systems are generally around 1.5-2kWp
(kilowatts peak), enough to provide almost half of the average
family's annual supply (assuming gas is used for heating
requirements and there are no energy efficiency savings).
This array would typically cover 10-15m2 of roof area.
Solar PV installations should always be carried out by a trained
and experienced installer.
Energy from the sun has been harnessed for thousands of years.
We use this energy in three main ways and when talking about
solar energy it is important to distinguish between these three
types:
• Passive heat: This is the heat that we receive from the sun
naturally. This can be taken into account in the design of
buildings so that less additional heating is required.
• Solar thermal: Where we use the sun's heat to provide
hot water for homes or swimming pools. We cover this
topic in another fact sheet: solar water heating.
• Photovoltaics (PV): Uses energy from the sun to create
electricity to run appliances and lighting. PV requires only
daylight - not direct sunlight - to generate electricity.
How PV technology works
Photovoltaic systems use cells to convert solar radiation into
electricity. The PV cell consists of one or two layers of a
semiconducting material, usually silicon. When light shines
on the cell it creates an electric field across the layers,
causingelectricity to flow.
The greater the intensity of the light, the greater the flow of electricity.
The three main types of solar cells are:
• Monocrystalline: made from thin slices cut from a single
crystal of silicon. This has a typical efficiency of 15 per cent.
• Polycrystalline: made from thin slices cut from a block of
silicon crystals. This has a typical efficiency of around 12 per cent.
• Thin Film: made from a very thin layer of semiconductor
atoms deposited on a glass or metal base. This has a
typical efficiency of 7 per cent.
Individual PV cells are connected together to form a module.
Modules are then linked and sized to meet a particular load
(need). The result is a PV array which supplies power to the
building it is fitted on. If the building has mains electricity, any
excess electricity can be exported to the national grid.
Alternatively, when demand is high, extra electricity can be
purchased from the national grid through the utility
companies. Where there is no mains supply, PV arrays can be
used to charge batteries.
PV arrays now come in a variety of shapes and colours,
ranging from grey 'solar tiles' that look like roof tiles, to
panels and transparent cells that you can use on
conservatories and glass to provide shading as well as
generating electricity.
Applications
There are many applications for PV, ranging from calculators,
solar torches and battery chargers to integrated systems for
homes, offices, factories and public buildings. You can use
PV systems for a building with a roof or wall that faces
within 90 degrees of south, as long as no other buildings or
large trees overshadow it. If your roof surface is in shadow
for parts of the day, the output of the system decreases.
Another consideration is that your roof must also be strong
enough to hold the significant weight of the panels,
especially if they are going to be placed on top of existing tiles.
Domestic installations
The size of a PV array required to provide electricity for a typical
home varies, depending on a number of issues; how much
power you need, the type of cell used, roof space available and
budget. Typical systems are generally around 1.5-2kWp
(kilowatts peak), enough to provide almost half of the average
family's annual supply (assuming gas is used for heating
requirements and there are no energy efficiency savings).
This array would typically cover 10-15m2 of roof area.
Solar PV installations should always be carried out by a trained
and experienced installer.
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