Thursday, May 31, 2012

Difference between Heat Pumps and Diesel or Gas Fired Boilers

In years gone by heating sources for large volume Commercial/Industrial Water Heaters have mainly been in the form of diesel or gas fired boilers.   These systems have always been afflicted with some disadvantages such as heating inefficiencies and the rising cost and the vulnerability of supply in some cases for these fuel types.  In addition there has also been a need to duplicate these systems with stand-by units to ensure continuous operation in the event of a breakdown or maintenance requirements.   The heating inefficiencies are caused – because only a low percentage of the gross energy that is produced from “burning” the diesel or gas, is actually transferred to the water or other fluid that is being heated.   This percentage of energy input can be between around 75% for new systems down to as low as under 50% for older systems.  The main cause of energy inefficiency in diesel or gas fired systems is that a good proportion of the heat that is generated through the burning process of these fuel sources is dissipated into the atmosphere through the flue pipe or chimney.   Further inefficiencies (up to an additional 30% reduction) can be experienced if the diesel or gas fired systems (in a Hotel for example) are required to heat the water to steam (100ºC) and then that steam is directed to a calorifer type storage tank to produce potable water at 60ºC for circulation to the various fixture points.    
In most cases when a diesel or gas fired boiler is initially installed it has to be duplicated with at least one additional identical system as a stand-by unit that will be able to handle the full hot water load requirement when the primary system requires repair or maintenance.   During these repair or maintenance periods the complete diesel or gas fired system is totally shut down and cannot contribute in any way to the heating requirements of the project; therefore the need for a stand-by unit.   However, the larger Commercial/Industrial Heat Pump products that are now available are normally fitted with multiple Heat Pump modules in the one unit that are digitally controlled in such a way that they can operate individually or together at any given time.   Provided the Heat Pump daily run cycle design is done correctly for each project there is usually no requirement to include any stand-by units thereby contributing positively to the reduction in capital cost and subsequently having a positive effect on the ROI equation.   The design of the system is critical in order to maximize the daily run cycle and at the same time keeping the daily run cycle at a suitable operational percentage that will allow the system to still contribute effectively even if one of the Heat Pump modules is isolated for service or maintenance at any time.  The non requirement of stand-by units for the Heat Pump alternative also reduces the amount of occupied floor space required in the building to house the heating systems.
Finally, a Heat Pump solution also provides a positive effect on the operating cost due to the energy efficiency of its design.   Whilst diesel or gas fired boilers produce a negative Coefficient of Performance (COP) because of the various heat losses that are experienced during their operation, a Heat Pump will actually produce a positive COP that provides a heating output in the form of hot water of somewhere between 360% to 400% more than the energy that is actually consumed by the system depending upon regional ambient and humidity weather conditions.   Heat Pumps are also capable of operating effectively in most areas of the World during the daytime, night time, or rainy and cloudy periods.  
Mel Peatey

Thursday, May 10, 2012

Heat Pumps compared to Solar Water Heaters

An Air to Water Heat Pump provides an ideal energy efficient hot water system alternative for both domestic household use, or for larger Commercial applications.  In reality a Heat Pump provides slightly less energy savings when compared to a domestic solar water heater, but there are a number of other significant advantages associated with the use of an Air to Water Heat Pumps.

One major advantage of the Heat Pump is the aesthetic appearance that is gained by not needing any thermal solar panels and in some cases a storage tank on the roof of the building to ensure efficient operation.  In some cases roof structures may have to be reinforced when they are required to support the weight of a domestic sized solar storage tank that can weigh in excess of 400 kg.  In addition, the installation cost of an Air to Water Heat Pump is very simple compared to the installation cost of a solar water heater, and this significantly lower installation cost for the Heat Pumps should also be taken into consideration when assessing the overall installed cost of either product alternative.

Another advantage of the Air to Water Heat Pump is the low energy input from the electricity supply that is required to operate the system, while at the same time producing an output of around 3 times more than the actual electrical input, when operated in average ambient temperatures of 20 degrees Celsius.  This results in an energy saving (reduction) of approximately 75% when compared to traditional electric water heaters.  In Regions where the average ambient temperature is higher than 20 degrees Celsius the actual energy savings can be higher due to the extra heat energy that is available from the ambient air in these locations.  Air to Water Heat Pumps do not require direct sunlight to operate efficiently because they collect free energy from the ambient air.    Contrary to popular belief, a solar water heater does requires back-up electrical energy to operate the booster element during periods of inclement weather, low radiation periods, and at night time when there is a need to supply hot water during those times.  When comparing similar volumes of hot water delivery the annual booster or back-up energy needed to ensure solar thermal water heaters provide a continuous supply of hot water during all weather conditions, or if hot water is needed during the evening period, is similar to what is expended annually for a Heat Pump to drive the evaporator fan and compressor.   A domestic sized Heat Pump could, in some cases, operate from Photovoltaic (PV) solar cell system due to the low energy input needed when compared to the actual output that is delivered in the form of hot water.  This makes the Heat Pump products ideal for isolated and heavily forested locations such as remote Eco Resorts.

By Mel Peatey.

Friday, May 4, 2012

Benefits of using Integrated Heat Pumps for Small Commercial Installations

Integrated Heat Pumps that are designed with a storage tank and heat pump module in one unit can definitely be an economically viable option to provide hot water for small commercial installations such as single block multiple level hotels with up to 100 accommodation rooms or in some cases even up to 150 rooms.    Provided there is sufficient floor space to locate the Heat Pumps and the proposed design (number of units) is correct the integrated models can provide a complete solution of hot water storage capacity as well as multiple heat pump modules that allow flexibility to maintain total hot water load requirements to be maintained even during periods when some units could be undergoing servicing or maintenance.

For example if a quantity of integrated systems were designed with sufficient units to meet all of the hot water demand criteria for a particular project and based on a 70% daily run cycle it would mean that the total heating capability of the combined units would be 30% above what is actually required on a daily basis.   Therefore the equivalent number of integrated heat pumps that represents 30% of the total could be isolated for a period of time while servicing or maintenance was carried out and the rest of the integrated heat pump units could still meet all of the daily hot water requirements for the project.   This design also removes the requirement to install additional stand-by units therefore reducing the capital costs and subsequently improving the return on investment (ROI) for the installation.

The plumbing pipe work connection design for multiple integrated heat pump installations is simple and straight forward with the main considerations being the use of reverse return pipe work which basically means that the first integrated heat pump unit that the cold water supply pipeline is connected to should be the last unit that the hot water delivery is taken from.   In addition the geometry as well as the length of branch connections off the main header pipe line to each integrated heat pump unit should remain the same in order to provide a balanced cold water flow and hot water delivery and ensure that each integrated heat pump unit contributes equally to the overall hot water requirement.  

By  Mel Peatey