Renewable Energy Sources (Pt 2)

Transcription

1 Renewable Energy Sources (Pt 2) Course to be taken after Part one - Understanding The Environment and Renewable Energy Sources. CPD = 2.5 hours. Introduction This course aims to look at alternative renewable energy sources, how they work, how they operate and how they are being implemented into the common domestic household. Some renewable sources may be unrecognisable say ones that are used by large utility companies and fed through to homes via the normal routes for gas and electricity and such. But understanding what renewable sources are being utilised by these utility companies will give a DEA further knowledge of how energy changes are being made and the affects these changes have to RDsap calculations. The UK Householder

2 With fuel prices rocketing in recent years and more public awareness of environmental issues, as well as more access to funding for greener living, more and more home owners are looking at cheaper and greener ways in which to heat and light their properties. As of 6th April 2008, a homeowner will not need to obtain planning permission for certain types of energy efficient equipment, including solar panels, so long as the property does not have listed building status or is in a conservation area. The first part of this course looks at the cheaper, do it yourself aspects of renewable energy sources, the difference they make to energy consumption and the environment, how they can be recognised by a DEA and of course the impact they could have on the energy rating of a property. Solar Heating & Hot Water

3 Solar water heating uses the radiation from the sun to heat water in a panel system which is often sited on the roof of a property. Solar panels can in turn supply both heating and hot water to a property, however unfortunately, the demands on a central heating system is usually at its highest when the sun is at its weakest, so a solar heating system will only contribute to part of your heating energy requirements and are mainly used for hot water purposes only in the UK. If the system is sized correctly, it can provide a third of all of your hot water requirements throughout the year. The average solar panel system will reduce Carbon dioxide emissions by around 325kg per year and will cut fuel bills by around 50 per annum. How Solar Power Works There are three main components for a solar water heating system:

4 1. The solar collectors these are the panels fitted to the roof and there are two main types of collectors: Tube system solar collectors these are rows of glass tubes that contain absorber plates that feed into a mainfold which then transports the heated liquid Flat plate collectors these are large absorber plates with a transparent cover that collects heat from the sun 2. A Heat Transfer System which uses the collected heat to heat the water 3. A Hot Water Cylinder A secondary water tank, usually installed at the same time as the solar panels, which holds the heated water until such time when it is needed. Photovoltaic's

5 Definition of a Photovoltaic Cell A photocell in which an electromotive force is generated by photovoltaic effect. As part of an inspection of a property, a DEA will need to recognise what a photovoltaic (or PV as it is commonly abbreviated to) panel looks like and the percentage of roof space in which the PV panels cover. It is not required for a DEA to know how PV panels work, but a basic working knowledge needs to be understood, along with an understanding of the impact that PV panels in situ at a property will have on an Energy Performance Certificate for future RDsap purposes. Commonly abbreviated to PV, photovoltaic's is a technology where light is directly converted to electricity by using solar cells packaged in PV modules. The solar cells produce direct current from light which can then be used as power. The cells require protection from the environment and are therefore packaged behind a glass sheet. What is Photovoltaic Energy? And Why is it Needed? Photovoltaic technology makes use of the suns energy to generate electricity. PV cells are commonly used in small everyday devices such as calculators, watches and torches but have recently started to be

6 used for objects such as parking maters and road signs, in which PV cells are place on such objects to generate their own electricity and to help reduce the demand on the grid. The ability to generate electricity directly from sunlight is a relatively new technology that offers new opportunities to generate green electricity. Solar photovoltaics offer the ability to generate clean, green and renewable electricity, therefore without producing harmful carbon dioxide emissions, which is one of the main gases affecting climate change. Ho w do PV Cell s Gen erat e Pow er? The photovoltaic process converts sunlight directly into electricity, by the sunlight striking the PV cell and in turn generates electricity.

7 Solar cells are made of a special type of silicone, that is melted and then built up of two or more thin layers. Each layer is given an opposite charge, one positive and one negative. When the sunlight strikes the solar cell, electrons are knocked loose and move towards the front cell. This then creates an electron imbalance between the front and the back of the cell and this causes electricity to flow. PV cells work on direct sunlight and therefore the greater the intensity of light, the greater the flow of electricity. Photovoltaic's & Housing

8 Assuming that PV cells are to be put into place on a house, there are certain other equipment needed to support the PV cells. They are: Charge Controller This regulates the flow of electricity from the PV cells to the battery and load. This helps to keep the battery charged but without over charging it. Batteries These are sometimes needed to store electricity for use during times when it is needed or to help meet the needs when the PV cells are not generating enough electricity to meet requirements. An Inverter Is needed to convert direct current (AC) into alternating current (DC) A Meter Is required to ensure that the system owner is credited for any excess power generated by the PV cells and fed back into the mains grid.

9 Making the Best Use Out Of PV Panels Of course effectiveness and efficiency of a PV system depends on a series of variable circumstances, such as: Location The amount of sunlight available will affect the

10 amount of energy produced Orientation The orientation of a building and the positioning of the solar arrays are vital to maximise energy production. In most of the northern hemisphere, a south facing façade will collect most light throughout the year and therefore produce more energy. Did You Know? Photovoltaic technology has its origins from space technology and the International Space Station has its own solar power system that has been specifically designed to power satellites in space! Wind Turbines This is a brief run down on residential wind turbines, how they work and how to identify them. We will go into wind power in more detail later in this course. In recent RDsap changes, there is the option to record whether a wind turbine is present or not, as well as the terrain type of the area in which the property is situated, which then in turns will

11 calculate whether a wind turbine should be added as a recommendation to making the property more energy efficient. How Wind Turbines Work Wind power is a clean, renewable source of energy which produces no carbon emissions or waste products from its use and could be a leading renewable energy in the residential home. Most wind power is generated in the form of electricity. Large scale wind farms are connected to electrical grids. The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity. So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

12 A 3 bladed wind turbine is the most common modern design for wind farms in the UK at present. Inside a wind turbine Inside a Wind Turbine Description of the Mechanical workings of a wind Turbine Anemometer: Measures the wind speed and transmits wind speed data to the controller.

13 Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate. Brake: A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies. Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 55 mph. Turbines do not operate at wind speeds above about 55 mph because they might be damaged by the high winds. Gear box: per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes. Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity. High-speed shaft: Drives the generator.

14 Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations per minute. Nacelle: The nacelle sits atop the tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on. Pitch: Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity. Rotor: The blades and the hub together are called the rotor. Tower: Towers are made from tubular steel (shown here), concrete, or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity. Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind. Other turbines are designed to run "downwind," facing away from the wind. Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.

15 Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind. Yaw motor: Powers the yaw drive. Small Scale wind turbines Small wind generation systems with capacities of 100kW or less are usually used to power homes, farms and small businesses. Isolated communities that otherwise rely on diesel generators may use wind turbines to displace diesel fuel consumption. Individuals are also purchasing these systems to reduce or eliminate their electric bills and to generate their own clean, green power. Types of Small Scale Wind Turbines There are two types of small scale (or domestic) wind turbines: Roof Mounted (top photo) These are usually installed upon the roof of the property. Mast Mounted (bottom photo) These are free standing wind turbines usually located close to

16 the building which it is providing electricity to. Small wind turbines generate power using direct current electricity. Systems that are not connected to the National Grid will require battery storage and an Inverter to convert the direct current electricity to alternating current. Most domestic wind turbines require planning permission to install and will require a professional wind turbine installer to check that the surrounding area, wind speeds and other certain elements will have an impact on the performance of the wind turbine Part Two Large Scale Renewable Energy sources The next part of this course looks at some of the larger and more expensive forms of Renewable energy sources being used around the world to save energy resources and produce less carbon emissions. Tidal Power Tidal Power, or tidal Energy as it is sometimes known as, is a form of hydro power that converts the energy of tides

17 into electricity or other useful forms of power. Although tidal power is not widely used, it certainly has the potential for electricity generation in the future. How Tidal Power Works There are two types of Tidal Power: Tidal stream systems - these make use of the kinetic energy of moving water to power turbines, in a similar way in which windmills use moving air. This type of tidal power is gaining popularity due to its low costs to build and maintain. Barrages Barrgaes make use of the potential energy in difference of height between high and low tides. Barrages are less popular to use due to very high infrastructure costs and a shortage of viable sites, as well as many environmental issues surrounding them. Tidal Power & Energy Efficiency Tidal power has an efficiency of 80% in converting the potential energy of water into electricity, which is just as efficient as solar power. How tidal Barrages work

18 Tidal Turbines This tidal turbine has been designed to be as simple and robust as possible. This keep up front costs down and also reduces the need for

19 expensive maintenance. The turbine unit can be fixed to the seabed and the rotor blades are designed to work in either tide direction meaning there is no need to rotate the whole unit, or the pitch of the blades when the tide turns. A (venturi shaped) duct is used to guide and accelerate the tidal stream toward the rotor. By using a duct, more energy can be extracted from the same amount of water with smaller diameter rotor blades thereby keeping costs of manufacture and maintenance down. Furthermore, even if the tidal flow is arriving at up to a 40 degree angle relative to the turbine rotor blades, the duct redirects the water so it arrives perpendicular to blades maximising generating efficiency. As the turbine rotor turns it powers a hydraulic pump which forces hydraulic oil though a hydraulic motor generator. This is a sealed system which will cope well with the harsh conditions 30m+ below the surface of the sea.

20 Biofuel Biofuel can be broadly defined as solid, liquid or gas fuel consisting of, or being derived from recently dead biological materials, but most commonly plants. Biofuel can be theoretically produced from any biological carbon source. The most common by far is photosynthetic plants that capture solar energy. Many different plants and plant derived materials are used for biofuel manufacture.

21 Biofuels are used globally and biofuel industries are constantly expanding in Europe. The most common use for bio fuels is as liquid fuels for automotive transport. The use of renewable biofuels provides increased independence from petroleum and enhances energy security. Biomass Biomass is material derived from recently living organisms. This includes plants, animals and their by-products. For example, manure, garden waste and crop residues are all sources of biomass. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal and nuclear fuels. There are also agricultural products specifically grown for bio fuel production, which include corn, switchgrass and soybeans. Biodegradable outputs from industry, agricultural, forestry and households can be used for biofuel production, either using anaerobic digestion to produce biogas, or using second generation biofuels; examples include straw, timber, manure, rice husks sewage and food waste. The use of biomass fuels can therefore contribute to waste management as well as fuel security to help prevent climate change, though alone they are not comprehensive solutions to waste management problems. Bioenergy From Waste

22 Using waste biomass to produce energy can reduce the use of fossil fuels, reduce greenhouse gas emissions and reduce pollution and waste management problems. Landfill sites generate gases as the waste buried in them undergoes anaerobic digestion. These gases are known collectively as landfill gas (LFG) This can be burned and is considered a source of renewable energy, even though landfill disposal are often non sustainable. Landfill gas can be burned either directly for heat or to generate electricity for public consumption. Landfill gas contains approximately 50% Methane, the same gas that is found in natural gas. Biofuels and Carbon Emissions Biofuels and other forms of renewable energy aim to be carbon neutral or even carbon negative. Carbon neutral means that the carbon released into the atmosphere during the use of fuel is reabsorbed and balanced by the carbon absorbed by new plant growth. These plants are then harvested to make the next batch of fuel. Carbon neutral fuels lead to to net increases in human contributions to atmospheric carbon dioxide levels, reducing the human contribution to global warming. A carbon negative aim is achieved when a portion of the biomass is sued for carbon sequestration. Calculating exactly how much greenhouse gas is produced in

23 burning biofuels is a complex and inexact process, which depends very much on the method by which the fuel is produced and the assumptions made in the calculations. Conclusion We hope that you now have a better understanding of renewable energy sources, how they are obtained and how they are used by the average UK householder. No doubt, as RDsap becomes more sophisticated, A DEA will need to be able to identify, understand and record any renewable energy sources used within a household.