Energy Savings by CHCP Plants in the Hotel Sector
Combined Heating, Cooling and Power
CHP involves the simultaneous production of thermal and electric energy from the same primary fuel source. For a given application, this is achieved through one of a number of different electricity generation technologies in which heat is diverted part-way through the electricity production process and used to satisfy thermal requirements. From a thermodynamic perspective, CHP offers efficiency advantages relative to the available alternatives.
The efficiency gains represented by CHP may be significant, but will vary depending upon the technology and fuel source employed and displaced by CHP systems. An efficient CHP plant can convert approximately 85-90% of the energy content of the fuel into useful energy. Although a small part of the heat will be lost before the heat reaches the consumers the total efficiency will remain in the area of 80% or more.
Conventional electric production systems typically convert 30-40%, with new combined-cycle gas turbine systems capable of up to 55%. In the case that the heat demand will be covered by heat generation plants with an efficiency of 90% the total efficiency for the separate production of electricity and heat will be up to 70%.
The development of CHP offers high energy conversion rate and lower emissions of CO2 which is the most important greenhouse gas. Another opportunity that CHP offers is the development of decentralised forms of electricity generation providing high efficiency and avoiding transmission losses.
Summarising, optimised CHP is an environmentally friendly method of energy production, reducing fuel need and increasing competition in generation. For this reason it could be considered as a vehicle promoting liberalisation in energy markets.
CHP is a technique in use from industry for more than 50 years. What is necessary for the user is to have medium or high demand for thermal energy (steam, hot water, hot gases, cooling etc.) over prolonged periods of time (more than 5000 hours/year). Power generation industry, manufacturing industry (chemicals, paper industry, iron and steel, ceramics, motors, food, textile, timber, bricks and heavy clays etc.) and service industry (hospitals, sport centres, hotels) are areas where CHP systems are an option for the investors.
Industrial CHP installations can operate for 8000 hours/year or more. Therefore, in industrialised countries, the heat potential in industry is large enough to enable CHP to provide a significant proportion of the base load demand for electricity.
District heating and cooling (DH&C)
District heating or cooling means centralised production and distribution of thermal energy. The heat is produced in thermal plants, and is circulated through a pipe network to the users in the form of steam or hot water. The DH&C system can be thought as the sum of the production facilities and distribution/return network. The most common competitor to DH are individual heating systems. A considerable number of DH schemes continue to be supplied by heat only boilers. However DH has become is a major application of CHP and extensive large systems have been developed in Scandinavia, Germany and central/eastern Europe.
These are mostly owned and operated by municipal authorities and can be fed by waste incineration plants and other means including geothermal heated heat pumps. In addition, district cooling offers considerable potential in Europe. With recent developments in engine and gas turbine technology, there is now great potential for the development of more localised DH/CHP systems - sized to meet the heat demand - and serving smaller heat distribution networks. The penetration of CHP in DH is different in the Member States, rising from 22% in France to 92% in the Netherlands (percentage of DH systems running in CHP mode).
In several Member States electricity consumption for cooling produced by compression equipment can reach 50 % of total electricity consumption in summer. The coexistence of District cooling and Heating systems can achieve significant reductions in costs by transforming part of the electricity consumption into heat consumption and increasing the working time of the CHP/DH systems.
Residential and commercial
These CHP systems are used in hotels, sport and leisure centres, hospitals and multi-residential accommodations. They are smaller units comprising a diesel engine which has been converted to run on natural gas, a generator and a heat recovery system, generally housed in a container. The diesel engines can also be dual-fuelled.
The heat recovery is via the engine's cooling circuits and its exhaust. To ensure a high availability of electricity there must be a simultaneous use for the heat or heat storage facilities.
A method increasing the use of recovered heat is to produce cooling using absorption chillers. This allows the CHP system to run during the summer months, when the lower demand for heating would otherwise reduce the opportunity for system operation.
For larger building complexes, gas turbines and larger reciprocating engines are used, as in industry.
Since the efficient use of energy reduces the emission of pollutants (CO2, SO2, NOx etc.) to the atmosphere, it is recognised as the single most important policy objective in attaining the E.U.'s stated objective of stabilising CO2 emissions. CHP is one of the very few technologies which can offer a significant short or medium term contribution to the energy efficiency issue in the European Union and can make a positive contribution to the environmental policies of the EU. According to estimations and in comparison to separate production of heat and electricity, the CO2 savings from 1 MWh of CHP electricity production vary from 132 kg to 909 kg with a reasonable average of 500 kg saved CO2 per MWh.
In 1994 the electricity generation by U.E countries CHP plants was 207 TWh (9% of the total electricity generation in 1994). With 29 GWe of new CHP installed capacity (conventional wisdom scenario) or 48 GWe (pre Kyoto scenario) in the period 1994-2010 this production could reach the 11% or the 14% respectively of the total electricity generation in 2010. The Commission believes that this anticipated growth has to be reached and if possible exceeded. A significant effort is required to achieve significant results. According to analyses made, a doubling of the current share of CHP from 9% to 18% of the total gross electricity generation of the Community produced by CHP by the year 2010, is realistically achievable.
This would imply doubling the existing installed CHP electrical capacity and increasing the annual load factor by 30% and would require that Member states remove the various obstacles to greater penetration of CHP in their energy systems. The environmental benefits would be significant. A rough estimate indicates that if a doubling of CHP share were achieved, considered as replacement of existing electricity and heat production plants, could reduce CO2 emissions by 150 Mt. per year or approx. 4% of the total E.U. CO2 emissions in 2010.
Despite this, the penetration of CHP in the E.U. (expressed as the CHP electricity production by private and public utilities as a fraction of the total electricity production) had decreased in the period 1974-1990. The electricity production by CHP plants in the European Union is disappointing and varies significantly between Member States, from 1% to 40%. Only in recent years has this negative trend been reversed.
While CHP technologies are generally quite mature in their development, and are widely used under full market conditions, there is a continued need for their further technological development. The European Parliament has recognised this fact and asked the Commission to encourage the 'wider application of CHP technology'.
These developments include improvements to cost effectiveness, adaptation to new types of application, integration of non conventional fuel process (renewables, gasified coal, landfill gas, waste,...) and improvements to combustion systems to meet tightening emissions standards. Without such development, the use of CHP may not be extended and may not be adjusted to the continuously energy market.
A doubling of the current share of CHP from 9% to 18% of the total gross electricity needs to plan a large development of CHP in E.U. Member States residential and commercial sectors.
In fact these sectors use 53 % of electrical energy produced in U.E but show a very low diffusion of CHP plants, though this technology is very attractive for hotels, hospitals, large administration buildings etc.
The installation of cogeneration systems is viable for hotel of a certain size and system of functioning.
Hotels should be medium-sized or large and not seasonal in type, as the number of hours of functioning have a decisive influence on the viability of cogeneration systems.
A hotel is a building designed to provide rest and comfort. Energy in different form is used in many hotel facilities and services to help create an atmosphere of comfort and therefore, after staff, it makes up the largest proportion of hotel running costs.
A rough estimation (based on some case studies) on the CHP energy saving effects shows primary energy supplied reductions varying from 12% to 50% with a reasonable average of 20%
Appropriate projects, co-operation and exchange of information can improve CHP in hotel sector and, according to previous U.E. estimations, a new 9% of the total electricity consumption covered by CHP by the year 2010, is realistically achievable.
Eurotel capacity in 1991 : 4421 thousands of beds Surface of hotel per bed : 40 m2
Energy consumption/m2 year
Maximum minimum Average electricity 250 kWh electricity 60 kWh electricity 100 kWh total 550 kWh total 120 kWh total 220 kWh
Total annual energy consumption in U.E. Hotels:
electricity : 17,684,000 MWh total : 38,904,800 MWh Power : 3000 MW
The energy saving potential of U.E. hotel is 0,2*38,904,800 MWh =7,780,960 MWh
Possible new CHP plants until 2010: 270 MW
New electricity produced by CHP: 1,591,560 MWh
Average of CO2 saved per MWh : 500 kg
Average of CO2 saved: 7.957,800 tons/year