Feasibility study of an energy supply system possibilities of a hotel

1. OBJECTIVES

1. Obtain information, build the systems, simulate (EES), and get results for the three systems.
2. Compare results of different solutions.
3. Evaluate different solutions advantages and drawbacks, and select the appropriate one according to established parameters.

2. DESCRIPTION OF THE SYSTEM

For this project it was selected the city of Nantes, to evaluatethe feasibility of a hotel. This facility has 200 guest room, public and conference rooms, restaurant, swimming-pool, wellness, kitchen and laundry. The objective is to investigate and evaluate energy supply possibilities of this hotel on three different configurations and compare them among them.

3. SYSTEM CONFIGURATIONS

* First Configuration for heat and cool supply:

The firstsystem is a traditional energy supply with heat generation by means of natural gas fired boiler, cooling and air conditioning by means of conventional vapor compression chiller and all the electricity is purchased from the district grid.

The following figure illustrates the system:

Fig 1: Sketch of the first heat and cooling production system

* Second Configuration for heat, cool andpower supply:

The second configuration has an internal combustion engine (ICE) which is the prime mover of a tri-generation system (CCHP). The priority of this CCHP system is to fulfill the heating and cooling demands of all facilities. The generated electricity is a by-product that could or could not satisfy the energy demands. In the case that the ICE doesn’t supply the electricity demands,the missing amount of electricity will be purchased from the district grid.

The following figure illustrates the CCHP system:

Fig 2: Sketch of the second configuration. CHCP system

* Third Configuration for heat, cool and power supply:

The third configuration is an Organic Rankine Cycle (ORC) tri-generation system, which uses peat as fuel. In the case that the ORC system doesn’tsupply the electricity demands, the missing amount of electricity will be purchased from the district grid.

The following figure illustrates the ORC system:

Fig 3: Sketch of the third configuration. ORC system

Biomass used in France is mainly fire-wood; sawmill by-products, black liquor and urban waste. Based on this, wood was selected as the biomass/fuel for our third system.
* ORCWorking fluid selection:
Cyclohexane was selected as the ORC working fluid based on our own analysis using EES due to the relatively high efficiency achieved using Cyclohexane (12,5%) when using heat source temperatures in the range of 573 K compared to other working fluids usable at this range of T (such as n-octane and toluene with energy efficiencies of 7,7% and 9,3% respectively for ourspecific operational conditions). Another advantage of Cyclohexane is its relatively high critical point (558 K) compared to other refrigerants typically used in ORC systems (such as R134a, R245fa and n-butane with critical points of and 375 K, 429 K and 426 K respectively).

4. SYSTEM ASSUMPTIONS AND INPUT DATA

* General Assumptions:

1. All facilities are operated all over the year.2. Heating and cooling demands were calculated based on the Heating Degree Days (HDD) and Cooling Degree Days (CDD) respectively.
3. The meteorological information was taken for Nantes during the year 2010.
4. All the systems are model in steady state conditions.

* Assumptions for the first configuration:

1. The flue gas form the boiler delivers enough heat to warm thespaces (rooms, laundry, kitchen, swimming pool) and heat water for internal consumption (30 m3 /day).
2. Fresh water is injected in the same volumetric ratio, in order to maintain a constant system.
3. The vapor compression system provides cool air, which prime mover is a compressor, which works with the electricity purchased form the grid.
4. All of these calculations were done by...