U3 Bit at the End type shi

Heat management

• Bulk storage of hot fluids

• Use of heat exchangers

• Combined Heat and Power (CHP) systems.

• Bulk storage of hot fluids

Reducing the surface area by using a large tank rather than multiple small tanks to store hot fluid will reduce heat loss.

Surface area and heat loss

Surface area and the resulting heat loss can also be reduced by changing the shape of a tank or container, for example, a sphere has the smallest surface area for any volume.

• Use of heat exchangers

Heat exchangers can be used for ventilation with minimal heat losses.

How do heat exchangers work?

The heat of the air leaving the building is passed to the air coming in.

The counter current flow of stale and fresh air in the heat exchanger ensures efficient heat transfer

• Combined Heat and Power (CHP) systems.

CHP power stations recover much of the heat lost in electricity generation and uses it for space heating in buildings, like homes, fish farms, and greenhouses.

What’s the maximum efficiency of a modern thermal power station when converting combustible energy or nuclear fuel into electricity using steam turbines?

40%

What happens to the remaining 60%?

The remaining 60% is lost as waste heat energy, mainly through the cooling water used to condense steam, through cooling towers, or into water bodies.

What do CHP stations do?

In many CHP stations, the efficiency of electricity generation is deliberately kept below 40% to increase the temperature of the hot water and increase its usefulness.

Name the electricity infrastructure management:

• High voltage grid

• Peak shaving/pumped storage HEP

• The use of ICT to co-ordinate data on electricity supply and demand and plan supply changes

• Locational factors affecting the development of new generating infrastructure

• High voltage grid. What was wrong with electricity flowing through a cable?

The resistance to the flow of electricity in a cable causes a loss of electrical energy as it is converted into heat which is lost from the cable.

What causes the loss of heat energy from cables?

The loss of energy is actually related to the amount of electricity flowing

What does the high voltage grid do then?

Electricity grids use transformers to control the current and voltage of the electricity distributed in the grid to minimise energy losses.

The National Grid

The national grid transports electricity at a very high voltage so that the current can be reduced to minimise energy loss, whilst maintaining the power delivered.

• Peak shaving/pumped storage HEP.

• The use of ICT to coordinate data on electricity supply and demand and plan supply changes.

ICT systems make it possible to accurately predict demand for electricity and monitor and adjust electricity supplies quickly.

Why are ICT systems good?

This reduces the waste of energy caused by generating electricity for which there was no demand.

• Locational factors affecting the development of new generating infrastructure.

The electricity generating equipment that is used in the future may be in new locations, for example, offshore windfarms rather than power stations on coalfields.

This will require the construction of new grid infrastructure.

Use of Materials / Construction Methods with Low Embodied Energy:

• Low embodied energy materials

• Earth-sheltered buildings.

• Low embodied energy materials

Many buildings require large amounts of cement for mortar and concrete.

The manufacture of cement requires a lot of energy so buildings that use cement have a high embodied energy.

Alternative materials that have lower embodied energy values are available

What are the alternative materials?

• Limecrete. Limecrete has half the embodied energy as concrete

• Rammed Earth

• Straw

• Earth-sheltered buildings

During cold weather, the ground is usually warmer than the air and the flow of the air over a building increases heat loss

Why are Earth sheltered buildings pretty dece?

Sinking some of the building into the ground can reduce heat losses.

Use of Materials with Low Thermal Conductivity / Transmittance?

• Double/triple glazing.

• Low emissivity glass.

• Vacuum/inert gas double/triple glazing.

• Wall/floor/roof insulation.

• Double/triple glazing.

Multiple layers of glass with spaces between them reduces the energy loss through windows

• Low emissivity glass.

This type of glass has a surface coating that reflects long wavelength infrared energy back into the building.

• Vacuum/inert gas double/triple glazing.

A gap between the panes filled with inert gases is more expensive but it has lower thermal conductivities

What’s the issue with wide vacuum gap in glazing?

It is not practical to have a wide vacuum gap because the panes need to be held apart with spacers which cannot be long, so vacuum double glazing is used where there is not space for gas filled multiple glazing.

• Wall/floor/roof insulation.

Most insulating materials reduce conduction by trapping airspaces in a porous structure

What do the most effective insulating systems have?

Prefabricated boards with a reflective foil layer to reflect infrared radiation.

Low environmental impacts of insulating materials

Some have low environmental impacts because they’re manufactured from waste, such as straw.

Name some design choices for buildings:

• Orientation/features for passive solar gains.

• Low surface area: volume ratio.

• High thermal mass materials

• Orientation/features for passive solar gains.

Energy losses are generally greater through windows than through walls

Solar gains through a window depend upon its orientation in relation to sunlight.

Northern hemisphere

Passive solar gains through windows are greatest through south facing windows, while losses are greatest on the north side of the building.

Different types of rooms

The use of a room may affect the area of windows needed and the room temp.

Different room types can be positioned in ways that would reduce overall energy use.

Rooms that need to be warmer may be placed on the side of the building that has greatest passive solar gains.

• Low SA:V ratio.

The shape of a building and whether neighbouring buildings are joined affects the surface area through which heat can be lost.

Buildings with a low SA:V will lose heat less easily

• High thermal mass materials

Temperature management in buildings can involve resisting periods of overheating and periods of low temperatures.

Using materials with a high thermal mass can help to reduce temperature extremes.

They can absorb heat to reduce over heating or emit heat to reduce heating requirements

Which materials have high thermal mass?

Concrete, water

Energy management technologies

• Occupancy sensors.

• Improved insulation.

• Automatic/solar ventilation.

• Heat exchangers.

• Lighting: CFL, LED.

• ‘Low-energy’ white goods.

• Occupancy sensors.

Sensors that detect movement in a room and turn lights on or off according to this.

• Improved insulation.

Most insulating materials reduce conduction by trapping airspaces in a porous structure

Improved insulations has prefabricated boards with a reflective foil layer to reflect infrared radiation.

What’s another benefit of improved insulation?

Some of the insulating materials have low environmental impacts because they’re manufactured from waste, such as straw.

• Automatic/solar ventilation.

Large glazed areas increase passive solar gains.

This may be excessive during very sunny weather

Overheating can be reduced using thermostatically operated automatic screens, self opening windows, and solar screens

• Heat exchangers.

Heat exchangers can be used for ventilation with minimal heat losses.

How do heat exchangers work?

The heat of the air leaving the building is passed to the air coming in.

The counter current flow of stale and fresh air in the heat exchanger ensures efficient heat transfer

• Lighting: CFL, LED.

CFL lamps are replaced with LED lights

• ‘Low-energy’ white goods.

White goods:

• Washing machine

• Dishwasher

• Refrigerator

• Washing machine

Faster spin cycles so the clothes need less drying

Cold and low temperature wash cycles which use less energy to heat water

• Dishwasher

Newer dishwashers use less water so less heating is needed

• Refrigerator

Low energy fridges have a more efficient compressor, like a linear compressor.

This doesn’t need oil lubrication as the pumped fluid acts as the lubrication.

This reduces maintenance and increases reliability.

It is also much smaller and so it has a lower embodied energy

Name the Transport Infrastructure & Management systems:

• ITS

• ATM

ITS stands for what?

Integrated transport systems (road, rail, cycle)

ATM stands for what?

Active Traffic management (smart motorways)

What is ITS?

These involve designing interconnected and complimentary bus, rail and cycle networks to enable people to get to their destinations via a public travel network.

What is ATM?

This system involves using variable speed limits on motorways to regulate traffic flow and minimise congestion. 'Smart motorways' involve the removal of the hard shoulder to widen the motorway to increase traffic flow.

Why should vehicles be designed for end of life?

Traditional vehicle design focuses on the ease of manufacture of components and their assembly to create the vehicle.

A newer concept is to design vehicles to minimise the ev impacts of the disposal of vehicles when they are scrapped.

Name some ways vehicles can be designed for end of life:

• Use of recyclable materials.

• Easier component identification.

• Easy dismantling/material separation.

Vehicle design for use:

• Aerodynamics/hydrodynamics.

• Low mass.

• Tyre/wheel design.

• Kinetic Energy Recovery System (KERS)/ regenerative braking.

• Use of low embodied energy materials.

• Bulk transport systems.

• Aerodynamics/hydrodynamics.

Reducing friction as a vehicle moves through the air or water reduces the amount of energy needed to propel it.

• Low mass.

Reducing the mass of the vehicle will reduce fuel consumption

How can the mass of the vehicle be reduced?

• Plastics are used instead of metals in areas where strength is less important

• Cast iron engine blocks can be replaced with lighter aluminium ones

• Designing vehicles with rounded 3D surfaces rather than angular corners creates a smaller SA so less material is needed and weight is reduced

• Tyre/wheel design.

Rotating pneumatic (air-filled) tyres deform under a vehicle's weight, generating frictional heat.

Underinflated tyres waste more energy.

Solid wheels lose less energy but give a bumpier ride unless used on rails like trains.

• Kinetic Energy Recovery System (KERS)/ regenerative braking.

• A technology that captures and stores energy that would normally be lost during braking in vehicles

• Instead of wasting the energy as heat, the technology saves it and then uses it to boost the car's acceleration later.

• The stored energy used for acceleration reduces the amount of fuel used

• Use of low embodied energy materials.

Materials can be used that require lower amounts of energy to manufacture.

Most of the energy used by a vehicle during its life is the energy to propel it, but a significant amount is in its embodied energy.

For a typical car, this is equivalent to its fuel consumption for 1.5 years.

If the car is made with recycled materials, then its embodied energy will be much lower.

• Bulk transport systems.

Transporting large quantities of resources simultaneously meaning that less energy is used per unit transported.

What is the cause of fluctuations in energy supply?

The use of intermittent energy resources

What are the causes of fluctuations in energy demand?

• Weather-related fluctuations

• Seasonal fluctuations

• Weekday/weekend fluctuations

• 24 hr work fluctuations

• Short-term fluctuations: mealtimes/TV ‘pickup’.

• 24 hr work fluctuations

There’s lower industrial demand outside core working hours

What do base load power stations do?

Base-load power stations generate electricity 24h a day, even though much less electricity is needed during the night, because it is uneconomic to turn the power stations on and off.

• Short-term fluctuations: mealtimes/TV ‘pickup’.

Fluctuations in demand. During meals or TV breaks, there’s a higher industrial demand.

The demand for electricity may drop more rapidly than power station output can be reduced

Name the developments in energy storage technologies:

• Peak shaving using Pumped-Storage HEP

• Rechargeable batteries

• Fuel cells

• Compressed gas

• Types of Storage Systems

• Peak shaving using Pumped-Storage HEP

1. Surplus electricity is used to pump water from a lower reservoir to a higher one

2. The energy stored as gravitational potential energy

3. Water is released when there is an increase in demand

4. It is rapid response

• Rechargeable batteries

Batteries that enable the original chemicals to be reformed using electricity so that the batteries can be reused

What factors affect rechargeable battery viability?

Energy density

Cost per unit of energy stored

Recharging speed

Examples of rechargeable batteries

Lead acid

NiCad (Nickel-cadmium)

• Fuel cells. What is a fuel cell?

Am electrochemical device the produces electricity from a chemical reaction (usually between hydrogen/alcohol and oxygen.

What do fuel cells require?

They require new fuel and oxidant chemicals to continue to operate

• Compressed gas

Surplus energy can be used to drive a pump that compresses air.

Compressed air can be released later to power machinery.

Where do large scale systems get their compressed air?

Underground caverns like in salt mines

How much power could large scale air compression systems produce?

200 MW

What can compressing the air also produce?

Heat

How are compressed gas systems made efficient?

The system will have a heat storage. This can recover over 90% of the original energy.

• Types of Storage Systems

• Thermal storage

• Vehicle to grid systems (V2G)

• Power to gas systems (P2G)

• The ‘hydrogen economy’.

• Thermal storage

• Heat energy is lost through conduction, convection, and radiation, making long-term thermal storage difficult.

• However, short-term storage can be efficient using molten salt, high-volume water, or high thermal mass materials

• They all have a high specific heat capacity, so the greatest possible amount of heat energy can be stored in a given volume

• Vehicle to grid systems (V2G)

• If vehicles are parked for long periods, then they should be plugged into the grid

• Peak in demands for electricity mean that a small proportion of energy from the vehicle battery may be used

• Surplus energy can then be used to recharge vehicle batteries

Why is the Vehicle to Grid system good?

Avoids the cost and ev impacts of using rapid response-low efficiency-high cost power stations such as “Open Cycle Gas Turbines”

• Power to gas systems (P2G)

Surplus electricity is used to produce gaseous fuel which can be stored

• It does this by using the surplus electricity to electrolyse water, splitting it into hydrogen and oxygen

• Hydrogen can be used to produce methane that can be fed into the natural gas pipe network

• The ‘hydrogen economy’.

The hydrogen economy is where surplus energy is stored as hydrogen, then used during high demand or low supply.

Storing excess energy helps manage intermittent energy supplies like solar and wind.

Why hydrogen?

Unlike many renewable energy resources, hydrogen has a high energy density and therefore could replace fossil fuels for many uses (such as powering vehicles)

What is a benefit to the hydrogen economy?

It reduces the energy losses created during energy conversions.

• If primary energy were converted directly to produce hydrogen, it reduces energy losses that would take place during multiple energy conversions.

What could the stored hydrogen power?

• Heating

• Vehicles

• Steam-turbine power stations

• Fuel cells to generate electricity.

Name the electricity infrastructure management:

• High voltage grid

• Peak shaving/pumped storage HEP

• The use of ICT to co-ordinate data on electricity supply and demand and plan supply changes

• Locational factors affecting the development of new generating infrastructure

• High voltage grid. What was wrong with electricity flowing through a cable?

The resistance to the flow of electricity in a cable causes a loss of electrical energy as it is converted into heat which is lost from the cable.

What causes the loss of heat energy from cables?

The loss of energy is actually related to the amount of electricity flowing

What does the high voltage grid do then?

Electricity grids use transformers to control the current and voltage of the electricity distributed in the grid to minimise energy losses.

The National Grid

The national grid transports electricity at a very high voltage so that the current can be reduced to minimise energy loss, whilst maintaining the power delivered.

• Peak shaving/pumped storage HEP.

• The use of ICT to coordinate data on electricity supply and demand and plan supply changes.

ICT systems make it possible to accurately predict demand for electricity and monitor and adjust electricity supplies quickly.

Why are ICT systems good?

This reduces the waste of energy caused by generating electricity for which there was no demand.

• Locational factors affecting the development of new generating infrastructure.

The electricity generating equipment that is used in the future may be in new locations, for example, offshore windfarms rather than power stations on coalfields.

This will require the construction of new grid infrastructure.