Micro Combined Heat In Uk Residential Areas Environmental Sciences Essay

Combined heat and power or cogeneration is the concurrent production of heat and electricity. CHP technologies produce electricity, heating and cooling from fuels such as natural gas or renewable – including landfill gas or biodiesel – at or near facilities like industrial complexes or commercial buildings. That is important because almost 70 percent (Roth, 2005) of the energy used to generate electricity at today’s conventional power plants is lost in conversion, delivery and distribution. That means only about 30 percent reaches its destination as useable power (Roth, 2005). CHP systems recover the heat that would normally be wasted in conventional electricity generation. They then use the energy from that heat to cool and heat their facilities. Of course, they also save the cost of the fuel that a separate unit would use to produce heating or cooling. CHP systems come in many sizes, from residential systems that generate one kilowatt of electricity to heavy industrial installations that can produce up to 25 megawatts.

In a typical CHP, such as a gas fired CHP, gas is burned in a combustion chamber. This creates a steady flow of hot gas that drives a turbine, which is coupled to a generator, thus producing electricity. As the gas is heated it is captured by a heat recovery boiler. The boiler then heats water which is pumped through insulated pipes providing space and water heating as required. In warmer countries were air conditioning is often used, the waste heat can also drive an absorption chiller to produce cold air. This is known as ‘trigeneration'(Bex, 2008).

2.3 Global Warming

Global warming describes the greenhouse effect. Certain gases allow short wave radiation to pass through them unabsorbed while also absorbing some long wave radiation that gets reflected back into space (Knol, 2009). Greenhouse gases trap heat the way glass walls of a green house do causing the Earth’s temperature to raise.

For thousands of years, emissions of greenhouse gases to the atmosphere have been well balanced by the amount of greenhouse gases that get naturally absorbed. These conditions have allowed human civilisation to develop within a consistent climate. Evidence shows that human activity contributes to global warming by adding to and changing the levels of the gases responsible for the greenhouse effects. Changes that have historically taken thousands of years are now taking place over decades. Rapidly retreating glaciers in countries such as Greenland, Alaska, Antarctica and on high tropical mountains show that global snow is melting and that massive glaciers worldwide are disappearing fast.

As water flows to the seas from melting glaciers and icecaps, causing a rise in sea levels. If this continues highly populated cities like Tokyo, Bangkok, Shanghai and New York are all at risk of major flooding. Scientists predict that floods and droughts are likely to increase in number and severity and climate related diseases such as malaria can rise. (REFERENCE) Other signs of climate change are seen in drying forests and dying wildlife.

Methane, nitrous oxide and carbon dioxide (CO2) are just some of the greenhouse gases contributing to climate change.

2.3.1 Carbon Dioxide

Of all the greenhouse gases, carbon dioxide is the main culprit. CO2 accounts for the largest proportion of greenhouse gases and contributed around 77 percent of the UK’s total emissions of greenhouse gases in 1990 (REFERENCECCB). Currently, carbon dioxide is responsible for around 60 percent of the ‘enhanced greenhouse effect’ (BBC, 2010).

Burning fossil fuels releases carbon dioxide. Fossil fuels are used to power cars, heat homes and give people electricity. Deforestation is also a major problem as the carbon dioxide stored in trees is released and also results in less carbon dioxide being removed from the atmosphere through photosynthesis. Atmospheric levels of carbon dioxide have risen steadily since the beginning of the industrial revolution and these levels are forecast to rise even more rapidly as the global economy grows (ASME, 2009).

Reducing the threat of global climate change starts with using clean energy options where available to reduce the emission of greenhouse gases. Such clean energy options include microgeneration technologies such as small wind turbines, heat pumps and micro combined heat and power systems.

2.3.2 UK Government Pledges

The Kyoto Protocol treated was agreed in Japan in Kyoto, Japan in December 1997. It came into force in on 16 February 2005.

The Kyoto Protocol is an international agreement linked to the United Nations Framework Convention on Climate Change. It is a legally binding agreement under which industrialized countries will reduce their greenhouse gas emissions by 5.2 percent by 2012 compared to the year 1990. The aim is to lower overall emissions from six greenhouse gases, including carbon dioxide. National targets have been set for countries worldwide, some of which include an 8 percent reduction for Australia, 6 percent for Japan, 10 percent for Iceland and 8 percent for the European Union (REFERENCE).

The 2006 UK Climate Change Programme, is designed to meet the UK’s Kyoto Protocol targets by reducing the emission of greenhouse gases by 12.5 percent between 2008 and 2012 (REFERENCE). This would also bring the UK closer to meeting their domestic target fo reducing carbdon dioxide emissions by 20 percent below 1990 levels by 2010 (REFERENCE). It also includes a goal the reduce overall carbon dioxide emissions by 60 percent by around 2050, with a significant reduction of around 26 percent by 2020 (REFERENCE). In July 2007 the Government’s Building A Greener Future: Policy Statement revealed that all new homes must be zero carbon from 2016 (REFERENCE).

To achieve these domestic targets, new low carbon technologies must be introduced in homes across the UK. Focusing on the manufacture and installation of microgeneration technologies seems the most probable route for the government to go if they are going to meet their targets.

2.4 Micro-CHP

Micro CHP is the simultaneous production of heat and electricity in a domestic or small commercial environment. They are generally run as heat applications, installed in the resident’s home, acting as a replacement for a conventional heating system such as a condensing boiler. Micro-CHP systems are currently based on several different technologies:

Stirling Engines

Steam Engines

Internal Combustion Engines

Microturbines

In a Micro-CHP system, a prime mover such as a Stirling engine drives a generator which produces electricity. The waste heat from the engine is used in the primary circuit of the heating system and the electricity generated is either used in the house or transferred back to the grid.

Micro-CHP systems are able produce heat at a very high efficiency of over 90% (Nottingham Energy Partnership, 2008) and utilise ‘waste heat’ to produce electricity as a by-product. This leads to a reduction in C02 emissions and may also drastically reduce energy bills, with a saving of 35% per annum being achievable (Cogen, 2009).

In the past and present, CHP has proven to be beneficial in many large-scale situations by increasing the overall thermal efficiency, reducing the total power requirement, and providing higher quality, more reliable power. Applying CHP technology to smaller scale residential and small commercial buildings is an attractive option due the large market potential. (Mado et al, 2008)

Figure 3 : Schematic of how energy flows in a micro CHP system

2.5 Marketability

Today, countries all over the world are worrying about the effects of climate change. Governments are providing major support in the design and manufacture of ‘greener’ technologies, all in aid of reducing in carbon dioxide emissions. They are encouraging people to go ‘greener’, and in some countries are providing financial support towards pushing micro-CHP systems onto the market. (CHPA, 2010)

The main target market for micro-CHP is the domestic market as a replacement for conventional gas boilers in domestic residences, with the Micro-CHP unit operating in a ‘heat-led’ mode.

The UKs domestic sector is responsible for 33.6 percent(REFERENCE) of the electrical usage. This is evident from the data provided in Figure 4 which also shows that the domestic sector makes up the largest portion of UKs electrical energy consumption.

Figure 4: UK Electrical Consumption by Building Sector

Figure 5: UK Electrical Consumption by Building Sector

The domestic energy consumption is not only the largest portion of the pie chart, but it is also the fastest growing segment. From 1961 to 2004 the number of UK households rose from around 16.5 million to 24.7 million (Office for National Statistics, 2005) and in 2009 projected figures published show an 30 percent increase in English households (CLG, 2009) and a 25 percent increase in Welsh households(W.A.G, 2009) over the next 20 years. Of the 24.7 million UK households around 14 to 18 million of these are said to be suitable for m-CHP units. (Cogen, 2005). Generally houses in the UK have low levels of insulation and therefore require higher levels of heating compared to much of north-west Europe (Cogen, 2005). Statistics show that only 14 percent of UK homes are fully insulated. Figure 6 shows that from 1970 to 2000 energy use for space heating has risen by 24 percent, for water heating by 15 percent, and for lighting and appliances by 157 percent. The only reduction was energy used in cookin which has fallen by 16 percent. (National Statistics, 2001)

Figure 6: Domestic final energy consumption by end use 1970 to 2000

There are approximately 17 million gas-fired central heating systems in the UK and approximately 1.3 million gas boilers are sold each year (Cogen, 2003).

These figures show the large potential market for Micro-CHP in the UK.

2.4.1 UK Government Financial Aid

The domestic Micro-CHP market is supported by the UK government who help fund public bodies that are in support of a more energy efficient UK. Two of these main public bodies are the Carbon Trust and the Energy Saving Trust (Act On CO2, 2008). In April 2005, the UK Government stated its intentions to support the demand of this up-and-coming technology by reducing VAT on Micro-CHP units from 17.5 percent to 5 percent (Cibse, 2005). On 1 April 2006, the Department for Trade Industry announced phase one of its £80m to suport the take-up of microgeneration technology under the Low Carbon Building Programme (Cowburn, 2008).

On 5 February 2010, the Government recognised the importance of Micro-CHP technology and announced its financial support for the technology through its ‘Clean Energy Cashback Scheme’ (also known as the Feed-In Tarrif) (REFERENCEcashrewardformchp).

Graham Meeks, Director of the CHPA (Combined Heat and Power Association), said: “Support uner the Feed-In Tarrif is vital in the early stages of commercialisation for micro-CHP, and today’s announcement is a step in the right direction. It will help secure the UK’s world-leading position in this exciting low-carbon technology, whilst giving householders a cost-effective choice in cutting their carbon footprint.” (REFERENCEcashreward)

The Feed-in Tariff (FiT) scheme is the first phase of the Government’s Clean Energy Cashback programme, and came into effect on the 1st April 2010 (Energy Saving Trust, 2010). It will provide a financial incentive for small scale, low carbon electricity generation. The FiT is mainly intended as a means of encouraging adoptions of green microgeneration technologies. The scheme has the potential to revolutionise the way consumers use and generate energy.

How the Scheme Works

If you are eligible to receive the FiT then you will benefit in 3 ways:

1. Generation tariff – a set rate paid by the energy supplier for each unit (or kWh) of electricity you generate. This rate will change each year for new entrants to the scheme (except for the first 2 years), but once you join you will continue on the same tariff for 20 years, or 25 years in the case of solar electricity (PV).

2. Export tariff – you will receive a further 3p/kWh from your energy supplier for each unit you export back to the electricity grid, that is when it isn’t used on site. The export rate is the same for all technologies.

3. Energy bill savings – you will be making savings on your electricity bills , because generating electricity to power your appliances means you don’t have to buy as much electricity from your energy supplier. The amount you save will vary depending how much of the electricity you use on site. (REFERENCE, energy savings trust)

2.5.2 Current Market Situation

In 2002 it was estimated that there were around 1000 Micro-CHP systems in operation in the UK. The majority of these systems were Whisper Techs “Whispergen” Stirling engine and Senertech Dachs reciprocating engines (Wikipedia, 2009).

At present, Stirling Engines, Organic Rankine Cycle and Internal Combustion Engines dominate the near-market (Dijkstra, 2009). However, only one company is close to exploiting the UK domestic market. The reason for this is other leading companies are targeting small commercial businesses and places like sheltered housing accomodation with larger units (Cogen Europe, 2004).

WhisperGen who have joined forces with one of the UKs leading power and gas companies E-ON (Micro Power, 2004) are at the forefront of the UKs domestic market. However, at present, they are not currently delivering any units to customers, although they are working towards a full market roll-out off mass manufactured units from 2011(E-ON, 2010).

2.5 Micro-CHP System Overview

Micro CHP is the simultaneous production of heat and power in individual homes; a unit which replaces the central heating boiler, providing heat and hot water as usual, but also generating electricity at the same time. It is not renewable energy (unless the fuel is renewable) but at least low carbon, and often lower carbon than some so-called renewable energy sources.

The majority of micro CHP systems today use natural gas as a fuel. The fuel is burned in the Stirling engine or other prime mover; the engine drives a generator which produces electricity for use in the home. Any surplus is exported to the network for use by others. Waste heat from the engine is used to heat water in the primary circuit of a hydronic, or radiator-based, central heating system. Depending on the type of prime mover, around 70% of the energy in the fuel is converted into heat, with 10-25% converted into electricity. Electricity is more valuable than heat, so there are substantial economic and environmental benefits compared with the separate production of heat in a boiler and electricity in a power station.

Smart metering – uk climate change programme

Cowburn D (2008). Microgeneration and why it is the future