Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece

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1 J. Energy Power Sources Vol. 2, No. 8, 2015, pp Received: August 3, 2015, Published: August 30, 2015 Journal of Energy and Power Sources Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece John Vourdoubas Department of Environmental and Natural Resources Engineering, Technological Educational Institute of Crete, Chania, Crete, Greece Corresponding author: John Vourdoubas (vourdoubas@chania.teicrete.gr) Abstract: Hotels utilize energy in various operations and electricity is the most widely used energy source. Hotel buildings are among the highest energy consuming buildings compared with residential, commercial or public buildings with an energy consumption of KWh m -2 per year. Due to the fact that energy cost is only a small fraction of their total operation cost in the range of 3-9%, little attention has been paid until today to use sustainable energy technologies in them. However, a combination of energy saving technologies and use of renewable energies in the hotels can cover all their energy needs, and zero the use of fossil fuels in them, which results in zeroing their CO 2 emissions due to energy use. Solar thermal energy, solar photovoltaic and low enthalpy geothermal energy with heat pumps can generate heat, cooling and electricity in order to cover all the energy needs of a summer operating and grid connected hotel in Crete-Greece. The capital cost of the necessary renewable energy systems is not prohibitive and its annual energy bill will be zero. Since the hotel does not use fossil fuels its CO 2 emissions due to energy use are zero. These renewable energy systems are reliable and cost effective and their application will increase the competitiveness of the hotel among environmentally conscious tourists. Keywords: Hotels, geothermal heat pumps, renewable energies, solar energy, solid biomass, zero CO 2 emissions. 1. Introduction A study on the use of renewable energies in hotels has been presented [1]. The authors investigated the possibility of using five different renewable energy technologies in the hotel sector: solar passive, hot water production with solar energy, solar Photovoltaics, geothermal energy and biomass. They concluded that the most popular renewable energy technologies were solar thermal, solar PV and geothermal heat pumps and the solar thermal applications had the lowest payback period. A study of energy performance of hotel buildings in Hong-Kong has been presented [2]. The authors studied 16 quality hotels in Hong-Kong and they found that 32% of totally energy consumed was for air conditioning, 12% for lighting, 5% for lifts and escalators, 23% for systems and appliances using electric energy and 28% for cooking and hot water production. They found also that energy consumption in 16 hotels varied significantly with an average value 564 KWh m -2 compared with 401 KWh m -2 reported for USA, KWh m -2 for Ottawa, Canada and 715 KWh m -2 for London. An assessment of energy efficiency for the Antalya region hotels in Turkey has been reported [3]. Analyzing data from 32 hotels the authors found an average electricity consumption of KWh m -2 and LPG consumption 2.8 kg m -2. Another study concerning energy consumption in Mediterranean and Greek hotels has been presented [4]. Analyzing data of a deluxe hotel it has been found that 61% of the energy consumed was used in space heating and cooling, 18% for DHW, 9% for electricity and the rest 12% in other uses. A feasibility analysis of standalone renewable energy supply options for a large hotel in Australia has been reported [5]. The authors

2 302 Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece have considered generation of electricity with PV and wind turbines together with batteries and the necessary electronics. They found that hybrid wind turbines combined with a diesel generator are profitable having high net present values. Similar feasibility analysis for renewable energy options in Australia for a grid connected large hotel has also been reported [6]. It was found that wind turbines and PVs are profitable in grid connected large hotels but hydrogen fuel cells are not. An assessment of practices and technologies of energy saving and renewable energy sources in hotels in Crete has been presented [7]. It has been found that one third of the hotel buildings in Crete have not thermal insulation. Some of them have replaced electricity with Liquid Petroleum Gas (LPG) in the kitchen and they use smart keys in the rooms in order to reduce energy consumption. The most of the hotels have old air conditioning units which are energy intensive and their regular service prolongs their lives. The vast majority of Cretan hotels use solar thermal systems for the production of hot water for various uses. The energy conservation and retrofitting potential in Hellenic hotels has been reported [8]. According to this study the total energy consumption in Greek hotels is 273 KWh m -2 per year and it is one of the highest among all categories of Greek buildings (as an average from energy audits in 158 Hellenic hotels). The authors believe that the energy consumption can decrease by 20% if various retrofitting actions can be implemented. Energy consumption of hotels of Hilton international and Scandic in Europe has been reported [9]. Average consumption for Hilton international was KWh m -2. An evaluation of the energy consumption in Mediterranean islands hotels with a case study for Balearic islands hotels has been presented [10]. It has been found an average energy consumption in Balearic islands 15.4 KWh per night spent compared with KWh per night spent in Greek islands hotels. Energy consumption per sector in an old Balearic island hotel is 19% for water heating, 24% for cooling, 12% for lighting, 10% in kitchen and laundry and 35% in other uses. The highest energy consumption was due to electricity, 54%, to diesel oil, 36% and to gas-lpg, 10%. A comparison with a Greek hotel shows that energy consumption per sector in a Greek hotel is 35% for hot water production, 15% for cooling, 6% for lighting, 9% for laundry and kitchen, 22% for heating and 13% in other uses. An analysis on energy use by European hotels has been reported [11]. According to various data which have been presented in a meta analysis for most hotels energy use falls in the range KWh m -2 per year but the most hotels are in the range of KWh m -2 per year. The main energy consuming activities in a hotel are: Heating rooms Cooling rooms Lighting Hot water production Kitchen-laundry Swimming pool Others Space heating and cooling is the largest energy user in the hotels, consuming approx. 50% of it. Domestic hot water is the second largest energy user consuming up to 15% of it. Lighting consumes 12-18% of total energy consumption and the kitchen and laundry consume together with various other uses the rest of it. Energy efficiency and energy conservation in hotels has been reported [12]. It has been found that a large hotel with total energy consumption less than 365 KWh m -2 per year can be categorized as energy efficient hotel. In a standard 3 stars hotel located in Southern Europe total energy consumption was 171 KWh m -2 per year distributed as follows: Space heating 12%, space cooling 10.6%, lighting 11.80%, DHW 34.3%, kitchen 12.5% and various equipment the rest. A hotel which covers all its energy needs with renewable energies for heat and electricity generation which results in zeroing its CO 2 emission due to energy use in Crete has been presented [13]. In a survey of five hotels

3 Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece 303 in Crete where three of them were summer operating hotels it was found that total energy consumption was 149 KWh m -2 per year, and these hotels were using electricity, diesel oil, LPG and solar energy for covering all their energy needs. It has been reported also that energy cost is a small fraction of the total operating costs of hotels and it varies between 3-9% of them. 2. Energy Consumption in Summer Operating Hotels The main energy consuming activities in a hotel are space heating and cooling, lighting, hot water production, operation of the kitchen and the laundry, operation of various electric machines (lifts, valves, pumps, etc.) and other uses. The highest energy consumption in hotels is for air conditioning and electricity, heating oil and gas are used for that. For hot water production heating oil, gas or solar energy are used. In the kitchen and the laundry electricity and gas are mainly used and for lighting and the operation of various electric machines and devices electricity. Data from energy analysis in five hotels in Crete [13] have shown that electricity was contributing between 62.90% and 84.05% in their total energy consumption. Energy use in hotels varies significantly between different types of hotels and is affected by hotel size, class, number of rooms, customer profile, location, climate zone, quality of construction, services provided to the guests etc. Annual energy consumption in hotels varies depending on various factors and an average energy consumption in a summer operating Cretan hotel per category is presented in Table 1. Among renewable energies used in various Cretan hotels today, solar energy is widely used for hot water production and in few cases solid biomass for heat generation, as well as low enthalpy geothermal energy for heating and cooling them. The main fuels currently used in Cretan hotels are presented in Table 2. Table 1 Average energy consumption in a summer operating Cretan hotel per category. Category Energy (%) Air conditioning 50 DHW 15 Lighting 10 Kitchen-laundry 15 Others 10 TOTAL 100 Table 2 Main fuels which are currently used in hotels in Crete-Greece. Category Fuels Air conditioning, oil, gas DHW Heating oil, gas, electricity, solar energy Lighting Kitchen-laundry, gas Others 3. Use of Renewable Energies for Covering all the Energy Needs of Hotels in Crete-Greece Combined use of various renewable energies can cover all the energy requirements in grid-connected hotels in Crete, which results in zero CO 2 emissions due to energy use in them. Solar energy, solid biomass, wind energy and geothermal energy can be used in hotels for power and heat generation. (1) Solar thermal energy can be used either for space heating and cooling or for power generation. Solar irradiance is high in Crete varying from KWh m -2 per year and the use of various solar thermal systems is attractive. Passive heating and cooling systems for space heating and cooling are used in a small number of hotels. However, solar thermal systems are used broadly for hot water production which is used in the kitchen, in the laundry and the hotel rooms. It is estimated that more than 80% of the summer operating hotels currently in Crete are using solar thermal systems for hot water production. These systems can provide 80-90% of the hot water needed in the hotel, the rest is provided with gas, heating oil or electricity heaters. Solar cooling systems with absorption cooling exist only in two hotels in Crete and, due to reliability and cost reasons, and this technology is not used broadly. Solar

4 304 Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece thermal energy for hot water production is the most broadly used renewable energy in the hotel sector in Crete. It should be also noted that solar thermal energy in the hotel sector is used in Crete more than in various other Mediterranean countries like Spain, France and Italy, except Cyprus where solar thermal technologies are also widely used. There are few hotels in Crete with large solar energy fields, having solar collectors with surface more than 1,500 m 2. (2) Solar PV energy can also be used for power generation in hotels in Crete. The largest part of energy which is consumed in hotels is electricity. Solar-PV is a well-known and reliable technology and recently with high cost reductions in the prices of PV systems, generation of electricity with solar PVs is also cost effective. In Greece the net-metering initiative which has been launched recently allows the installation of PV cells in the hotels in order to generate the power which they consume annually since the PV generated and fed into the grid electricity will offset the yearly grid consumed electricity. Taking into account that a solar-pv system with nominal power 1 KWp in Crete-Greece will generate approx. 1,500 KWH per year, the PV system can be seized in order to generate annually the electricity which is equal to hotel consumption. Estimations prove that with current electricity prices in the hotel sector in Greece and the current low cost of PV systems such an investment in hotels is profitable. Current uses of solar energy in hotels in Crete are presented in Table 3. (3) Solid biomass can be used for heat production in the hotels. Local solid biomass sources like olive Kernel wood, a byproduct of olive oil producing industry in Crete has been used for that. Solid biomass can be used either for space heating or for hot water production in hotels. Its main advantage as a fuel is its low price compared with its heating value, which is much lower than the price of heating oil or gas. However, it is a rather dirty fuel creating during burning various pollution problems and a bad smell. Table 3 Current uses of solar energy in hotels in Crete. Solar energy technology Applications Passive solar Few applications for space heating and cooling Solar thermal heating Many applications for hot water production Few applications currently but Solar PV more are expected in the future through net-metering initiative Solar thermal cooling Only two applications Currently, there are only few hotels in Crete using olive Kernel wood for heating during the winter. Some large hotels in the island use liquid biomass for biodiesel production when they recycle the fried vegetable oils from their restaurants. Usually these fried oils are collected from various restaurants including hotels restaurants and they are used for biodiesel production in processing plants. (4) Low enthalpy geothermal heat pumps can be used in hotels for space heating and cooling as well as for hot water production. Heat pumps consume electricity but they have high coefficients of performance (C.O.P.) producing more heat and cooling than the consumed electricity. Geothermal heat pumps have C.O.P. in the range 3 to 4 or even higher and they can cover all the heating and cooling needs of the hotels. They utilize the heat of the ground or the heat of water in a well or in the sea which has an almost constant temperature all over the year and this increases the C.O.P. of the heat pump. In these cases a heat exchanger is placed few meters below the surface of the ground in order to exchange heat. The cost of geothermal heat pumps is higher than the cost of other heating systems using heating oil, gas, or biomass. Also it is higher from the cost of conventional air to air heat pumps. However, the fact that they use a clean source of energy like electricity favours their use in hotels to day. (5) Wind energy can be used for power generation in hotels when they are located in places with high wind potential and high average annual wind speeds. Wind turbines have the drawback that they need more often maintenance compared to photovoltaics. For Greece, the

5 Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece 305 Table 4 Renewable energies which can be used in hotels in Crete for covering their energy needs. Renewable energy Generated energy Solar thermal Space heating and cooling, DHW Solar PV Geothermal heat pumps Space heating and cooling, DHW Solid biomass Space heating, DHW Wind energy current net metering initiative allows only the installation of photovoltaic panels for offsetting the annual electricity consumption in a hotel. Therefore the use of photovoltaics is preferable compared to wind turbines for electricity generation in hotels. Hotel Stadthalle in Wien, Austria [14-15] is a good example of a hotel using a combination of various renewable energies in order to cover all its energy needs without using fossil fuels proving that it is feasible in a cost effective way. It uses solar thermal and photovoltaic panels, ground water heat pump and three wind turbines in order to have a zero energy balance generating annually the same amount of energy that it consumes and it also zeros its CO 2 emissions due to energy use. Various renewable energies [16] which can be used in hotels in Crete are presented in Table Design of a Hotel in Crete-Greece with Zero CO 2 Emissions Due to Energy Use A design of a grid connected summer operating hotel in Crete-Greece which covers all its energy needs with renewable energies resulting in zero CO 2 emissions is presented. The capacity of the hotel is 100 beds and its built surface 2,000 m 2. It is assumed that the hotel operates 200 days in the summer, its overall occupancy rate is 85% and its energy consumption is 16 KWh per night spent. The energy consumed in the hotel in various categories is the same as in Table 1. The characteristics of the abovementioned summer operating hotel in Crete are presented in Table 5. In order to cover all its energy needs with renewable energies, the following criteria must be fulfilled: The hotel must not use fossil fuels during its operation; Table 5 Characteristics of a summer operating hotel in Crete-Greece which covers all its energy needs with renewable energies. Number of beds 100 Built surface 2,000 m 2 Operating days 200 days/year Annual occupancy rate 85% Nights spent annually 17,000 Energy consumption 16 KWh per night spent Total annual energy consumption 272,000 KWh Specific annual energy consumption 136 KWh m -2 Energy consumption for A/C 136,000 KWh/year Energy consumption for DHW Energy consumption for lighting Energy consumption in the kitchen and the laundry Energy consumption in other uses 40,800 KWh/year 27,200 KWh/year 40,800 KWh/year 27,200 KWh/year Table 6 Energy generated from different renewable energy systems in the hotel. System Energy generated annually Solar Thermal 32,640 KWh Solar-PV 134,057 KWh Geothermal heat pump 144,160 KWh Total 310,857 KWh The grid electricity consumption annually must be equal with electricity which will be generated with a photovoltaic system located in the hotel and will be fed into the grid. It should be noted that this is allowed in Greece with the initiative of net-metering. Among renewable energies, solar thermal energy, solar-pv and low enthalpy geothermal energy will be used in the hotel in order to cover all its energy needs. It has been assumed that solar thermal energy will be used in order to cover 80% of the needs for DHW. Low enthalpy geothermal energy will be used for air conditioning and for covering the rest of the needs for DHW. Photovoltaic electricity will be used for the operation of the heat pumps, for lighting, for the operation of various machineries in the kitchen and the laundry and for other uses. The C.O.P. of the geothermal heat pump is assumed 3.5. The energy generated in the abovementioned hotel from different renewable energy systems is presented in Table 6. Comparing data from Tables 5-6 it can be seen that

6 306 Creation of Hotels with Zero CO 2 Emissions Due to Energy Use: A Case Study in Crete-Greece Table 7 Size of different renewable energy systems used in the hotel. System Size Unit cost Overall cost ( ) Area of solar thermal collectors 40.8 m m -2 10,200 Nominal power of PV KWp 1,200 /KWp 107,244 Power of the geothermal heat pump 60 KW 1,800 /KW 108,000 Total 225,444 Total per bed 2,254 Table 8 Annual CO 2 emissions due to initial use of fossil fuels in the summer operating hotel in Crete-Greece. Fuel Energy used Emissions of CO 2 (KWh/year) (Kg CO 2 /year) 210, ,481 LPG 61,200 14,076 Total 272, ,557 Total per bed 2,720 2,226 CO 2 emissions: = kgco 2 /KWh, LPG = 0.23 kg CO 2 /KWh the energy generated annually when only renewable energies are used in the hotel (310,857 KWh) is higher than the initially consumed energy when conventional fuels were used (272,000 KWh). The difference, 38,857 KWh, is the electricity generated from the photovoltaic system in order to power the heat pump. In order to size the renewable energy systems the following assumptions are made: Annual electricity generation for Photovoltaic cells in Crete is 1,500 KWh per KWp; The power of the heat pump will be double than the average calculated in order to cope with peak loads; 1 m 2 of solar collector produces in Crete 800 KWh of hot water during the operation of the hotel for 200 days in the summer period. The size and the cost of different renewable energy systems in the hotel are presented in Table 7. The use of renewable energies for covering all the energy needs of the hotel in Crete-Greece will result in zeroing its CO 2 emissions due to energy use. Assuming that the hotel initially uses LPG for producing hot water and covering the 50% of the energy needs in the kitchen and laundry, and electricity for covering the rest of its energy needs it will consume annually 210,800 KWh of electricity and 61,200 KWh LPG. The CO 2 emissions due to the consumption of those energy sources are presented in Table 8. Since the hotel will utilize only renewable energies for covering all its energy needs, it will zero its CO 2 emissions due to energy use. Therefore, it will save 222,557 kg CO 2 annually or 2,226 kg CO 2 /bed*year. 5. Conclusions Hotel buildings consume a lot of energy KWh m -2 compared with other buildings, and electricity is the main energy source that they use. Energy cost is only a small fraction of the total operation cost of a hotel in the range of 3-9% and this is the main factor that hotels pay little attention in the application of sustainable energy technologies in them. Renewable energies can be used in hotels for generating electricity, heat and cooling in a cost effective way. In Crete-Greece, solar and wind energy are abundant and significant amounts of solid biomass exist. Solar thermal energy is broadly used currently in hotels in Crete only for hot water production. Solar thermal and solar-pv energy combined with low enthalpy geothermal energy and heat pumps can cover all the energy needs of hotels in the island replacing fossil fuels in a cost effective way. This results in zeroing their CO 2 emissions due to energy use. The operation of a zero energy balance hotel in Vienna- Austria using renewable energies proves that this is currently feasible. An example of a middle size summer operated and grid connected hotel in Crete- Greece has been presented and the cost of renewable energy systems for obtaining a zero annual energy balance as well as the CO 2 emissions savings due to the use of renewable energies have been calculated. The renewable energies installation cost per bed for using only them is 2,254 and the annual CO 2 emissions saving is 2,226 kg CO 2 per bed.

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