Acc We Da3120 Energy Recovery Guidelines 1.0 Mar 08

ACC_WE_ DA3120_ENERGY RECOVERY Guideline 1.0 Mar 08

Hotel Technical Specifications

…DA 3120…

ENERGY RECOVERY Guidelines

International Edition 1.0 March 2008

This document is published by Accor exclusively for use on Accor projects. Distribution or reproduction (in full or part) for other uses is forbidden.

ACC_WE_DA3120_ENERGY_RECOVERY_Guidelines_1.0_Mar_08.doc 2/27

ENERGY RECOVERY

INTRODUCTION

INTRODUCTION

HEATING RECOVERY FROM AIR HANDLING UNIT

HEATING RECOVERY FROM GAS BOILERS SMOKES EXHAUST

1

2

3

4

5

HEATING RECOVERY FROM CHILLERS

HEATING RECOVERY FROM COOLING TOWERS

Chapter Contens

6 HEATING RECOVERY FROM STEAM CONDENSATES

7 SOLAR DOMESTIC HOT WATER PRODUCTION

8 WATER TEMPERATURES


SOMMAIRE

1 INTRODUCTION 4 1.1 GENERAL...........................................................................................................................................................4 1.2 general recommendations ...................................................................................................................................4 1.3 choice of solutions...............................................................................................................................................4

2 RECOVERY FROM AIR HANDLING UNITS 5 2.1 Basic principle.....................................................................................................................................................5 2.2 Adiabatic wheel (prefered solution)......................................................................................................................5 2.3 Heat PIPE ...........................................................................................................................................................5 2.4 Plate exchanger ..................................................................................................................................................5 2.5 Glycol water coil ..................................................................................................................................................6 2.6 Air/air heat pump.................................................................................................................................................6 2.7 Energy recovery from extracted air......................................................................................................................6

3 RECOVERY FROM GAS BOILER SMOKES EXHAUST 8 3.1 Principles ............................................................................................................................................................8 3.2 1-stage economizer.............................................................................................................................................8 3.3 2-stage economizer.............................................................................................................................................8

4 RECOVERY FROM CHILLERS FOR DHW PRODUCTION 10 4.1 The different solutions .......................................................................................................................................10 4.2 Chillers with desuperheater ...............................................................................................................................10 4.3 Chiller with total heating recovery system..........................................................................................................11

5 RECOVERY FROM COOLING TOWERS 12

6 ENERGIE TRANSFER WITH 4-TUBE HEAT PUMPS 13

7 RECOVERY FROM THE STEAM NETWORK 13 7.1 Principle ............................................................................................................................................................13 7.2 Recovery FROM the condensate tank...............................................................................................................13 7.3 Recovery FROM condensates at the exchanger output.....................................................................................13

8 THERMAL SOLAR HEATING FOR DOMESTIC HOT WATER 14 8.1 Objective...........................................................................................................................................................14 8.2 Principle ............................................................................................................................................................14 8.3 Recommendations ............................................................................................................................................14

9 PRINCIPLE DIAGRAMS 16

Complementary documents, especially • HVAC • DHW production • BMS


1 INTRODUCTION

1.1 GENERAL

This document expresses the intention of the Accor group to control energy. It is additional to the technical specifications of the group’s different brands concerning heating, air conditioning, domestic hot water production installations, etc. It is based on Accor’s experience in the construction and technical management of hotel services. It gives advice and recommendations that must be interpreted and adapted as a function of the reality of the project. It is addressed to MEP consultants that remain responsible for the project design.

1.2 GENERAL RECOMMENDATIONS • Avoid oversizing • Select an energy that is only slightly polluting • Use the most efficient machines • Avoid technical sophistication, the operator must be capable of understanding the

installations • The choice of the solution of heating systems and cooling systems must be made as a

function of the climate

1.3 CHOICE OF SOLUTIONS • Recovery from air handling units so as to reheat fresh air using energy from the

discharged air. This principle must operate inversely in the summer − By adiabatic wheel − By heat pipe (caloduc) − By plate exchanger − By glycol water coils − Air/air heat pump − Chiller in recovery from discharged air to preheat domestic hot water

• Recovery from gas boilers

− By the addition of a single-stage condenser economizer − By addition of a two-stage condenser economizer

• Recovery from cooling units

− Chiller with desuperheater − Total recovery chiller − Recovery from dry coolers

• Transfer of heat with 4-tube heat pumps • Recovery from steam network • Thermal solar heating for domestic hot water


2 RECOVERY FROM AIR HANDLING UNITS

2.1 BASIC PRINCIPLE

• Energy recovery from air extractions is compulsory • The choice of the solution takes account of:

− the configuration of rooms − possibilities of superposition of AHU and extractors.

• The most efficient solution will be chosen. When several solutions could be considered, a financial study will justify the choice.

• The recovery must operate efficiently in all seasons: − in winter to preheat fresh air using discharged air − In summer to cool fresh air using discharged air

• Recovery takes priority. Heating and cooling coils can only come into operation when recovery is functioning. Control is adapted accordingly

• Operation in free-cooling is an obligation whenever possible depending on outside conditions. Automatic controls are adapted accordingly.

2.2 ADIABATIC WHEEL (PREFERED SOLUTION) Solution applicable to AHU for guestrooms and for general services. It is compulsory in hot and humid countries, since the wheel can dehumidify incoming air. • The AHU and the extractor are superposed. • The efficiency of this solution is high: of the order of 75% • It must be preferred for humid countries so as to dehumidify incoming air. • The rotary economizer is driven with a variable speed motor. • A controller adapts the rotation speed as a function of the temperature and humidity of

the fresh air, extracted air and blown air. • Operation is suitable for summer and for winter. • Recovery is automatically stopped during spring and autumn. • Filters protect the economizer on the fresh air inlet and on the extraction. • A manometer checks the dirtiness of filters and the coil

2.3 HEAT PIPE Solution applicable to AHU for guestrooms and for general services. Placement of “horizontal” heat pipes can save height. • The AHU and the extractor are superposed (fresh air at the top and discharged air at the

bottom) or placed adjacent. • The efficiency of this solution is high: of the order of 65% • Operation is permanent and with no motor. A by-pass is installed to avoid using

recovery when it is not necessary (spring and autumn) and when it is required to use outside air for cooling.

• Operation is essentially for winter. • A filter protects the economizer on the fresh air inlet and on the extraction. • A manometer checks the dirtiness of filters and the coil.

2.4 PLATE EXCHANGER Solution applicable to AHU for guestrooms and for general services. • The AHU and the extractor are superposed or placed adjacent to each other. • The efficiency of this solution is of the order of 50% • Operation is continuous with no motor. A by-pass is used to avoid using recovery when

it is not necessary • Operation is suitable for winter and for summer. • Recovery is switched off during spring and autumn.


• Caution with frost in winter, which can block up the coil on the discharged air side in contact with fresh air at very low temperature. Fresh air needs to be heated before entering the economizer for very cold countries, and a frost free temperature has to be maintained at the inlet to the economizer.

• A filter will protect the economizer on the fresh air inlet and on the extraction. • A manometer will check the dirtiness of filters and the coil.

2.5 GLYCOL WATER COIL Solution applicable to AHU for guestrooms and for general services. • It will only be used for very large hotels in which it is very difficult to make intersections

between incoming and outgoing air flows in the same technical room. • It is not appropriate for hot countries • The AHU and the extractor may be at a distance from each other. • The efficiency of this solution is of the order of 40% • Operation is made using a circulating pump. It is possible to switch the circulating pump

off to avoid using recovery when it is not necessary and if it is required to use outside air for cooling.

• Operation is essentially for the winter. The gain in summer is low. • Caution with frost in winter. Glycol water shall be used. • This solution is not as efficient, but it can be used for a second recovery after the water

coil on the discharge duct (see below). • A filter protects the economizer on the fresh air inlet and on the extraction. • A manometer will check the dirtiness of filters and the coil.

2.6 AIR/AIR HEAT PUMP AHU including blowing and extraction will be equipped with a first recovery by static exchanger (wheel, heat pipe, plates), together with a reverse cycle heat pump used: • IN WINTER, to recover calories from air discharged after the static economizer in order

to heat fresh air. • IN SUMMER, SPRING and AUTUMN, to cool fresh air and remove calories from the

discharged air. This solution is very usefully applicable for the treatment of fresh air for rooms: the neutral air blowing temperature (about 20°) enables a high performance coefficient. Temperate climates will not need any complementary treatments. Heating or cooling coils will be essential for more extreme climates.

2.7 ENERGY RECOVERY FROM EXTRACTED AIR Install a low power water/water cooling unit that: • IN WINTER: Recovers calories from discharged air after the economizer to preheat

domestic hot water from 10°C to 50°C. • IN SUMMER and BETWEEN SEASONS: To cool the chilled water return, before general

production of cooling and to recover energy so as to preheat domestic hot water. The following is an example design

2.7.1 DOMESTIC HOT WATER NEEDS • DHW needs for a 100-room Sofitel are approximately:

− Peak: 21 000 liters per day − Average: 10 000 liters per day

• With permanent 24-hour reheating of water from 10°C to 50°C, the required power is of the order of:

− With maximum needs: 41 kW (21 m3 x 1.16 W/m3°C x (50°C – 10°C) / 24h) − With average needs: 20 kW (21 m3 x 1.16 W/m3°C x (50°C – 10°C) / 24h) − The heating power of the unit must be between 20 and 40 kW.


2.7.2 RECOVERY FROM DISCHARGED AIR (EXAMPLE ON ROOMS AFTER THE GLYCOL WATER COILS ) • Available power on discharged air

− Discharge air flow = 7 500 m3/h − Recovery with glycol water coils is 40% − Extracted air 22°C; fresh air in winter -5°C, dif ference = 27°C − With 40% recovery: 27 x 0.40 = 10.8°C − So, the discharge air temp. is 22°C – 10.8°C = 11. 2°C for outside air at -5°C.

• Selecting the chiller

− water / water with excellent efficiency − Powers considered for this example = Cooling capacity 23 kW for chilled water

at 4°C and heating capacity 34 kW for hot water at 55°C. Consumed electrical power = 11 kW.

− The delta temperature between extracted air and discharged air has to be kept at 9°C (23 kW / 0.34 W/m3°C / 7500 m3/h x 1000) . Operation of the unit is stopped when the air temperature at the output from the glycol water coil is less than (9°C + 4°C) = 13°C so that compressors do not start and stop continuously.

− Glycol water will be used for operation at a temperature below 4°C.

2.7.3 CONNECTION PRINCIPLE • Connection of recovery coil

− Chilled water coil, in the air extraction after the glycol water recovery coil. − Thermostat between the glycol water coil and the recovery coil. The

thermostat stops the cooling unit when the temperature drops below a threshold that would prevent permanent operation of the compressor.

− Coil condensate recovery tank and connection to the drain. • Chiller

− Caution, the water/water chiller is chosen as a function of the efficiency. − Built-in chiller control done with constant chilled water temperature (for ex 4°C).

• Connection between chiller and recovery coil

− Manual valves are closed in summer and open in winter. − Labels on «closed in summer » valves − Expansion vessel and valve for operation in winter − Flow controller

• Connection between chiller and chilled water distribution

− Isolating valves closed when recovery is performed − Labels on “closed in winter” valves

• Connection between chiller and DHW exchanger

− Primary exchanger carries water at 55/50°C and sec ondary exchanger carries DHW at 45/50°C

• Connection between DHW exchanger and tanks

− Storage volume to enable permanent and regular operation of recovery. The optimum volume is between 20 and 30% of the average daily consumption.

− Connection onto the cold water at the inlet to the first tank − Three-way motor driven modulating valve, sensor and controller to keep the

water return temperature on the exchanger equal to 25°C minimum. − Double circulating pump with electrical connections and operation and

inversion controls. • Circulating pump slave controls as a function of the chiller with timeouts when the chiller

is stopped.


3 RECOVERY FROM GAS BOILER SMOKES EXHAUST

3.1 PRINCIPLES

• The recoverable energy on the smokes exhaust is close to 10% of the boiler heating

capacity. • Recovery will be made in the case in which the installation has one or several low or

very low temperature distribution networks (the water returns at a temperature less than 50°C),

• Several networks are usually concerned: − Hot water supplies to fan coil units − Preheating of fresh air of the AHU − Preheating of domestic hot water

• The heat recovery system may be single stage or 2 stage, for example by combining a fan coil unit return on the first stage (water 40°C ) and preheating of domestic hot water on the second stage (water at 10°C).

• The study must demonstrate that recovery cannot cause any overheating in the networks used. All cases must be studied for winter, summer and for spring and autumn.

• Recovery shall be made from the exhaust gases flue with an energy exchanger installed on a branch connection so that recovery is possible using any boiler.

• The economizer is fitted with a fan slaved to operation of the boilers. A timeout enables operation of the fan a few minutes after the boilers are stopped.

• Exhaust gas flues and ducts will be made of stainless steel. • The power of the economizer will be chosen as a function of the recoverable power. • The water flow in the recovery system will be constant (no variable flow that could cause

overheating in the economizer). • Energy recovery device

− A slope shall be provided and there shall be a drain at the low point to collect all condensates.

− Two thermometers (on the input and output sides of the economizer). − Two temperature probes connected to the BMS to monitor recovery.

• The efficiency and the annual savings will be simulated taking account of the temperature of the exhaust gases and the water.

3.2 1-STAGE ECONOMIZER

• Water connections (for example on the fan coil unit water returns)

− Connection on the water return pipe before the three-way valve. − A flow controller with the fan slaved to prevent overheating. − A relief valve. − Two thermometers (on the economizer input and output sides) and two

temperature probes connected to the CTM to monitor recovery.

3.3 2-STAGE ECONOMIZER • The efficiency of the installation will be further improved if a second recovery stage is

added. • The first recovery stage is exactly as described above. • The second exchanger will operate with water at a lower temperature than the first

stage. It is suggested to use: − Preheating of domestic hot water: recovery is possible throughout the year. − Preheating of fresh air for AHU: recovery is only possible in winter.

• Water connections (for example: preheating of domestic hot water)

− The first tank is only used for preheating. − The capacity must be equal to 500 liters per 100 kW boiler heating capacity.


− A circulating pump slaved to operation of the boilers with timeout after stopping to prevent overheating.

− A relief valve. − Two thermometers (on the input and output sides of the economizer). − Two temperature probes connected to the CTM to monitor recovery.

• Consultancy − The domestic hot water preheating tank can be used in winter on exhaust

gases from gas boilers and in summer on energy released from chillers. − The installation is thus more efficient. − The economizer on exhaust gases is not used in summer.


4 RECOVERY FROM CHILLERS

4.1 THE DIFFERENT SOLUTIONS

• Chiller with desuperheater • Chiller with total recovery

4.2 CHILLERS WITH DESUPERHEATER

4.2.1 PRINCIPLE • At least two chillers • Recovery is done on a single chiller (possibility of fitting two chillers but with the second

in standby). • Permanent recovery when the chiller is in operation. • Low recovered power at partial load. • Recovery water temperature: 55/60°C. • Important: the return temperature must always be >= 50°C otherwise the chiller

efficiency will be reduced. • Use: In hot countries, in operation during most of the year.

4.2.2 DETERMINATION OF POWERS / VOLUME • Desuperheater recovery energy:

− about 25% of the chiller cooling capacity when the chiller is at full load. • DHW exchanger characteristics:

− Primary water temperature (chiller side): 55/60°C − Secondary water temperature (DHW side): 30 / 55°C

• Water flow between desuperheater and exchanger:

− Constant when the chiller is in operation − Gives a delta temperature of 5°C

• Storage volume

− Dedicated exclusively to storage of recovered heat − 20 to 30% of the hotel’s daily DHW needs

4.2.3 CONTROL

• The chiller keeps the chilled water temperature constant for the different needs. The

adjustment is made on the chiller logic controller. • A logic controller manages the recovery based on the following principle:

− The two circulating pumps start 30 seconds before the chiller so as to excite the flow controller.

− A timeout keeps the circulating pumps in operation for five minutes after the chiller has stopped.

− The three-way valve regulation maintains a minimum return temperature of 50°C to the desuperheater and a maximum temperature of 70°C to the preheating tanks.

• The terminal tanks provide additional heating for domestic hot water.


4.3 CHILLER WITH TOTAL HEATING RECOVERY SYSTEM

4.3.1 PRINCIPLE • Total recovery can preheat domestic hot water to a maximum temperature of 50°C, the

recovered energy is high. • This solution is compatible with an installation comprising a single chiller. • It is even more useful for installations with several cooling units. In this case, it is often

enough to perform recovery from a single unit. • A calculation note shall be produced, justifying needs and recoverable powers. • To optimize efficiency, the water return temperature to the condenser economizer shall

be: − As low as possible. Note that the efficiency for cooling with outside air at 30°C

is the same as with water at 45°C. − At least 25°C. The chiller will not work with a l ower temperature.

4.3.2 POWER / VOLUME

• Recovery energy

− The recovery power is the total power to be evacuated from the chiller (cooling power + electric compressor power).

• Characteristics of the DHW exchanger

− Primary water temperature (chiller side): 50 / 55°C − Secondary water temperature (DHW side): 30 / 50°C

• Water flow between the economizer and the exchanger

− Constant when the chiller is in operation − Gives a delta temperature of 5°C

• Storage volume

− Dedicated exclusively to storage of recovered heat − 20 to 30% of the hotel’s daily DHW needs

4.3.3 CONTROL IF DHW MADE WITH ELECTRICAL HEATERS IN TANK S

• The chiller keeps chilled water at a constant temperature for the different needs. The

adjustment is made on the chiller logic controller. • An independent logic controller manages the recovery • The tank 1 electric heater is used only as a standby and if there is a legionella

contamination to increase the tank temperature to 60°C. • The tank 2 electric heater is authorized to operate in off-peak hours. The logic controller

determines the start time such that the tank reaches a temperature 60°C at 6:00 in the morning at the beginning of the drawing-off period. (peak hours are depending the local electricity board )

• The last tank is always in operation at 60°C so as maintain the temperature loop. • Operation from 6:00 to 15:00: the temperature of tanks 1 and 2 is left to drift. • Operation from 15:00 until forced restart at night:

− When the chiller is in operation, recovery is authorized. Pump P1 is in operation, pump P2 is in operation, the three-way valve V1 regulates to maintain a minimum return temperature of 25°C on th e cooling unit economizer, the three-way valve V2 is open to tank 1. When the temperature of sensor S3 is greater than the temperature of sensor S2, water is transferred to tank 2, and if the temperature of sensor S3 is less than sensor S2, water is transferred to tank 1.

− If the cooling unit stops, recovery stops with all pumps stopping and the valves closing. Recovery is started again if necessary when the unit starts again.

− Recovery stops when all sensors in the recovery tanks are at 50°C. The cooling unit releases its calories to the outside.


− A new recovery cycle is authorized when the temperature S1 of tank 1 drops below 25°C.

• Control in winter

− The cooling unit is stopped. There is no possible recovery. − The tanks operate directly with the electrical heaters.

4.3.4 CONTRIOL IF DHW IS MADE WITH GAS OR URBAN NETWORK

• The chiller maintains a constant chilled water temperature for the different needs. The

adjustment is done on the chiller logic controller. • A logic controller manages recovery. • Heating of tank 3 is maintained permanently at 60°C using the exchanger. • Operation from 6:00 to 15:00: The temperature of tanks 1 and 2 is left to drift. • Operation from 15:00 to forced operation at night:

− When the chiller is in operation, recovery is authorized. Pump P1 is in operation, pump P2 is in operation, the three-way valve V1 regulates to maintain a minimum return temperature of 25°C on th e cooling unit economizer, the three-way valve V2 is open to tank 1. When the temperature of sensor S3 is greater than the temperature of sensor S2, water is transferred to tank 2, and if the temperature of sensor S3 is less than sensor S2, water is transferred to tank 1.

− If the cooling unit stops, recovery stops with all pumps stopping and the valves closing. Recovery is started again if necessary when the unit starts again.

− Recovery stops when all sensors in the recovery tanks are at 50°C. The cooling unit releases its calories to the outside.

− A new recovery cycle is authorized when the temperature S1 of tank 1 drops below 25°C.

• Control in winter

− The cooling unit is stopped. There is no possible recovery. − Tanks are heated using the exchanger, by modifying manual valves.

5 RECOVERY FROM COOLING TOWERS

5.1.1 PRINCIPLE

• Installations fitted with water / water cooling units located in a service room use a cooling

circuit at a temperature of 45/50°C and outdoor coo ling towers. • Cooling units operate at full power in summer and partially in winter. • Energy released by the cooling units must be recovered. • The heating recovery can be used for:

− Preheating of domestic hot water (needs are constant throughout the year). Recovery is done using a preheating tank dedicated to recovery. A temperature comparison will prevent recovery if the temperature of the hot water is higher than the cooling network.

− Hot water distribution to fan coil units. If the fan coil units operate at temperatures of 45/40°C, part of the heating in spr ing and autumn can be performed and possibly the temperature loop in summer can be maintained.

• In all cases, take care to maintain a minimum water return temperature of 25°C on the cooling unit condensers.


6 ENERGY TRANSFER WITH 4-TUBE HEAT PUMPS

• The SOFITEL standard scheme comprises: − Distribution of hot water for heating − Chilled water distribution.

• The 4-tube heat pump is capable of heating and cooling simultaneously on two distinct water circuits

• The 4-tube heat pump can: − Produce chilled water only, and release calories outdoors (conventional

air/water cooling unit). − produce hot water alone (air / water heat pump) − transfer calories (water / water) when there are any heating needs on the hot

water network and cooling needs on the chilled water network or vice versa. • The heat pump is regulated to two values. Firstly it keeps the hot water temperature at

one set value (for example 50°C) and secondly the c hilled water network at the other set value (example 7°C).

• Each heat pump is connected to a hot water buffer tank and a chilled water buffer tank so as to provide sufficient inertia for correct operation of the installation.

• An economic study could justify setting up a single 4-tube heat pump and a second 2-tube reverse cycle heat pump. The first operates throughout the year. The second operates only as a booster in the winter and in the summer. Adaptations are made on the pipes to facilitate season changes.

7 RECOVERY FROM THE STEAM NETWORK

7.1 PRINCIPLE

• This solution is applicable for Cities that have a heat distribution network in the form of

steam. • Heat is supplied in the form of steam and the return to central production is hot water at

a temperature of about 70°C. Heat is metered by me asuring the consumed water flow. • Recovery is made to preheat domestic hot water. • The quantity of heat is variable and takes account of building needs:

− In winter, consumption is high. − In summer, heating needs are low. They usually apply only to production of

domestic hot water. • In summer, it would be possible to use the recovery tank on recovery from cooling units.

This would make it possible to amortize the two installations more quickly.

7.2 RECOVERY FROM THE CONDENSATE TANK • A first recovery is made with a coil placed in the condensate tank. • It is connected to the cold water that supplies hot water tanks. • Recovery is done on a branch connection from the main pipe to avoid creating load

losses on the domestic hot water network. • A circulating pump maintains a permanent water flow.

7.3 RECOVERY FROM CONDENSATES AT THE EXCHANGER OUTP UT • All condensates that exit from the heating exchanger pass through a hot water buffer

tank • The volume of the recovery tank is depending on the size of the installation. • All cold water intended for domestic hot water production goes into the tank. • Recovery is important at times when DHW is being drawn off.


8 SOLAR ENERGY FOR DOMESTIC HOT WATER PRODUCTION

8.1 OBJECTIVE

• For preheating of domestic hot water throughout the year. • To be offered systematically in countries with long sunshine. • Must not be over sized. • Domestic hot water temperature in tanks must never exceed 80°C. • Solar panels shall be easy to access for maintenance.

8.2 PRINCIPLE • Production

− Flat panels or solar tubes on flat roof or on exposed walls. − Possible isolation of each panel. − Pipes to resist high temperatures, preferably in copper. − Use of a frost-resistant heat transporting fluid. − Hi performance thermal insulation of pipes. − Heat exchanger between the primary and domestic hot water. − Safety device to avoid exceeding 80°C in the tanks − Expansion vessel to enable large expansions of the heat transporting fluid.

• Storage − At least 1 tank reserved exclusively for solar recovery − Resistance of the inside coating to temperature (100°C) − Possibility of increasing the tank temperature to 70°C using energy in the case

of legionella. − Access manhole for maintenance.

8.3 RECOMMENDATIONS

• Increase collector height to enable renovation of the waterproofing on the flat roof. • Remember that hot water consumptions may be reduced on some days. • Use reliable tested processes • The various elements must resist high temperatures. Even if they are accidental or

occasional. • Take account of different climates (strong winds, rain, hail, etc.).


9 WATER TEMPERATURE

The inlet/outlet chilled water temperatures, the inlet/outlet water temperatures from the heating recovery system are important for the efficiency. Here under results on test done on factory. They are valid just for one type of chiller, but it is a good example and can be extrapolate on other equipment.

9.1 WATER TEMPERATURE 7/12°C COMPARE TO 10/15°C Here under test done on factory on one chiller. The letters in bolt are more realistic points, for ex at 20°C the chiller is 25% loaded only.

Outside T = 20°C Outside T = 28°C Outside T = 36° C Outside T = 44°C Chilled water

Chiller load

CL Pe EER CL Pe EER CL Pe EER CL Pe EER

100% 294 78 3.8 271 89 3.0 246 103 2.4 222 119 1.9 75% 230 56 4.1 214 65 3.3 195 75 2.6 174 86 2.0 50% 167 35 4.7 155 41 3.8 142 47 3.0 127 55 2.3

10/15°C

20% 74 17 4.3 69 20 3.4 63 23 2.7 56 27 2.1

100% 265 72 3.7 243 86 2.8 222 99 2.2 200 115 1.8 75% 208 54 3.9 193 63 3.1 176 72 2.4 158 84 1.9 50% 149 35 4.3 139 40 3.5 126 46 2.7 113 54 1.8

7/12°C

20% 66 17 3.9 61 20 3.1 55 23 2.4 49 26 1.9

CL = Cooling load in kW, Pe = electric power in kW Conclusions, to change from 7/10°C to 10/15°C the c hilled water temperature: • The cooling capacity of the chiller increases : about 10% • EER is improved: between 7 to 10% The condensates are reduced on the cooling coils, but the cooling capacity of the FCU is reduced. It is requested to increase the water flow and/or the size of the FCU.

9.2 DESUPERHEATER Here under test done on factory on one chiller (same machine as here above). The letters in bolt are more realistic points, for ex at 20°C the chiller is 25% loaded only. The water temperature at the desuperheater = 55/60°C (inlet/o utlet):

Outside T = 20°C Outside T = 28°C Outside T = 36° C Outside T = 44°C Chilled water

Chiller load

CL Rec EER CL Rec EER CL Rec EER CL Rec EER

100% 265 28 3.8 243 46 2.9 222 68 2.3 200 89 1.8 75% 208 18 3.9 193 31 3.1 176 47 2.4 148 64 1.9 50% 149 6 4.3 139 16 3.5 126 26 2.7 113 38 2.1

10/15°C

20% 74 3 4.3 69 8 3.4 63 13 2.7 56 19 2.1

CL = Cooling load in kW, Rec = energy recovery in kW Summary: • The cooling capacity of the chiller is not affected by the desuperheater, • The EER is not significantly increased, • The water temperatures (60°C) from the desuperheat er are very interesting from DHW

production, • Higher is the outside temperature, higher is the recovered energy,


• Higher is loaded the chiller, better is the recovery. Cf here under a summary:

Outside T Chiller load in %

Heating recovery in % of the

cooling load 20°C 20 4%

50 11% 28°C 75 16% 75 26% 36°C

100 30%

Conclusions, generally the desuperheating system: • Is not well appropriate for moderated climate countries • Is more appropriate for hot countries • Is badly efficient when the chiller is loaded between 0 to 50% • This solution is available in hot countries if the chilled water production is produced by at

least 2 chillers: the 1st one is quickly fully loaded and therefore is able to produce efficiently DHW

9.3 TOTAL HEATING RECOVERY

Here under test done on factory on one chiller (different machine as here above)

EER of the chiller, according both ways of working

The chiller runs on outside air

The chiller runs in recovery mode

Outside temperature in °C Water temp heating recov. in. °C Chiller Load 20 25 30 35 40 45 30 35 40 45 50 55 100% 4.4 4.0 3.5 3.0 2.6 2.2 5.5 4.8 4.1 3.5 3.0 2.5 75% 4.4 4.0 3.5 3.1 2.7 2.3 5.6 4.9 4.2 3.6 3.0 2.6 50% 4.1 3.7 3.3 2.8 2.4 2.0 5.5 4.7 3.9 3.3 2.7 2.2 20% 4.0 3.6 3.2 2.8 2.4 2.0 5.4 4.6 3.9 3.2 2.7 2.2

The recovery is efficient, the energy transferred is the total of cooling load and the electric consumption of the machine, whatever is the chiller load. According the needs, the chiller runs under 2 various modes: • “normal”, the cooling used the outside air. This mode is done when there is no more

needs to produce DHW. • “recovery”, the cooling is done by energy transfer to a plate exchanger where the DHW

is pre-heated. Analysis of the here above data: • EER is deteriorate when the recovery water temperature is too high, • Conversely EER is improved when the water temperature is not too high. • Between that, the “balance” points are around:

− EER on air at 30°C = EER on water at 45°C − EER on air at 35°C = EER on water at 50°C

For exemple if we keep only this last line, when the outside temperature is 35°C the production of water at 50°C is absolutely free. The global efficiency of the system is greatly improve. Conclusion : A total heating recovery system is generally a good solution

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ACC_WE_DA3120_ENERGY RECOVERY Guidelines 1.0 Mar 08

10 PRINCIPLE DIAGRAMS

Supply air

Extracted air

Fresh air

Extracted air

Fresh air

Supply air

Return air

Supply air

Return air

Fresh air

Extracted air

HEAT PIPES (caloduc)

ADIABATIC WHEEL

PLATE EXCHANGER

Return air

Cf § 2.2

Cf § 2.3

Cf § 2.4

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Return air

Extracted air

Fresh air

Supply air

HEAT PUMP AIR / AIR

GLYCOOL WATER COIL

Extracted air

Fresh air

Supply air

Extracted air

Cf § 2.5

Cf § 2.6

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Chiller in recovery mode

Valves opened in summer

Valves opened in winter

50°C 55°C

25°C mini

To DHW users

DHW return

Classical DHW production

Cold water

Extracted air

1 n

En. recovery coil

From/chilled water hotel network

6°C

11°C

Tank dedicated to energy recovery

AHU

C

RECOVERY ON EXTRACTED AIR FOR DHW

Heating recovery system

To/From heat production (boilers…)

Cf § 2.7

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Heat recovery equipment

Cold water

50°C mini

1 n

RECOVERY FROM GAS BOILERS SMOKES EXHAUST – 1 STAGE

Hotel FCU network

Classical DHW productio n

Exhaust gas flues

Exhaust gas flues

Boilers

1st stage recovery

Water return from FCU goes inside the heating recovery


To DHW users

DHW return

Cf § 3.2

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Heat recovery equipment

C

Cold water

1 n

RECOVERY FROM GAS BOILERS SMOKES EXHAUST – 2 STAGES

Hotel FCU network


Exhaust gas flues

Exhaust gas flues

Boilers

1st stage recovery

Water return from FCU goes inside the heating recovery

1

Heating recovery syste m

2nd stage recovery

50°C mini

To DHW users

DHW return

Cf § 3.3


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C

DHW return

To/From heat production (boilers…)

Cold water

To DHW users

> 50°C

Chilled water network

Desuperheater



To/from hotel network

CHILLERS DESUPERHEATERS

Cf § 4.2

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C

DHW return

To/from heat production (boilers…)

Cold water

To DHW users

25°C mini


Water condensor

To/from hotel network



CHILLER TOTAL RECOVERY

Cf § 4.3

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55°C 50°C CHILLER WATER / WATER

25°C mini

Heating recovery to FCU hot water return

FCU hot water network

40°C

45°C

Cold water

Dry cooler Dry cooler

Heating recovery to DHW production

RECOVERY FROM COOLING TOWERS

To/from boilers

CHILLER WATER / WATER

Cf § 5

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ACC_WE_DA3120_ENERGY_RECOVERY_Guidelines_1.0_Mar_08.do

Heat pump 2-pipes Heat pump 4-pipe

Opened in winter

Closed in summer

Heating network Chilled water network

ENERGY TRANSFER USING 4-PIPE HEAT PUMP

Cf § 6

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To DHW users

C

DHW return


Cold water

Condensates return


RECOVERY FROM STEAM CONDENSATES


Condensates tank C

Cf § 7

From hotel steam network

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To DHW users

C

DHW return

SOLAR DHW PRODUCTION

Tank dedicated to solar energy

Automatic control system

Expansion tank

Cf § 8

Cold water


Documents

Acc We Da3120 Energy Recovery Guidelines 1.0 Mar 08