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Introduction to Commercial Heat Pumps


There are several kinds of heat pumps, but they all operate on the same basic principle -- heat transfer. Heat pump systems use the traditional refrigeration cycle to do this, which is the same technology found in residential systems. This cycle can be used for heating or cooling, depending on how refrigerant flow is directed. The warm liquid refrigerant is directed to an expansion valve, which reduces refrigerant pressure, and therefore the refrigerant’s temperature. The refrigerant, now in a gaseous state, is sent to the evaporator coils and intake air is pushed over those coils to cool them. The cooled air is then sent to the proper zone for climate control. The warmed, gaseous refrigerant then goes to a compressor, where the pressure increases, and the refrigerant is changed back to a hot liquid. The hot, liquid refrigerant then goes to condenser coils, air is pushed over these coils and then direct out of the building to exhaust the heat. The cycle then begins again.


Most heat pumps contain a four main parts:

  • Condenser – A piece of equipment that condenses gas into a liquid. The process cools the material and allows the release of heat into the environment.

  • Expansion Valve – Regulates the flow of material injected into the evaporator.

  • Evaporator – Reverses the condenser by turning liquid into gas. This process causes the material to absorb heat from the environment.

  • Compressor – Reduces the volume of gasses and /or moves the liquid through the system.

  • Refrigerant – The liquid/gas moving through the system.


There are 3 Main Types of Heat Pumps:


1. Air Source heat pump (ASHP) is a system which extracts heat from outside air, or vice versa. Air source heat pump uses ambient energy from outside air for space heating, cooling, and hot water generation application. ASHP system contains refrigerant system comprising condenser and compressor which is used to transfer heat.


All-Air” systems are classified into 3 main categories:

  • Single zone is the simplest and most common of “All-Air” central system is a single duct, single zone system. This system is most commonly used in many sizeable single-story buildings such as supermarkets, discount stores, can be effectively conditioned by a series of single zone systems

  • The Dual-Duct system employs two air ducts: one cold air duct and another warm air duct from the air-handler to the conditioned spaces. This system is most commonly used in large corporate buildings with varied requirements of heating and cooling

  • Multi-zone System is an individual supply air ducts where cool air and hot (or return) air are mixed at the supply fan outlet and is distributed through the separate ducts to each zone. This system would be most commonly used in Offices, classrooms, hotels, ships etc. where individual control is required.

2. Water source heat pumps (WSHP) dissipate heat by way of water instead of air. They require well, lake, or other water source access, and are not as common. A WSHP is a type of heat pump that operates by rejecting heat to a water-pipe system (or water loop) during the summer or by absorbing heat from the same water loop during the winter. If multiple units of WSHPs are installed, they can all be serviced by a common water-loop system (or header). A water system is a good choice for office buildings, hotels, condominiums, libraries, and schools. Almost any type of commercial building that has several temperature controls zones, some of which need to be heated while others need to be cooled. Water source heat pumps (WSHPs) are able to draw their heat energy from a water source in two different ways, through an open loop system or closed loop system.


3. Open loop heat pump (using water as your primary energy source) - An open loop system draws in water from a water source, such as a borehole, river, or a lake, into the heat pump absorbing its energy as it passes through the system

  • Closed loop heat pumps (using a water-water heat pump as part of a heating system) - Beyond using water as the primary energy source from which heat is drawn, heat pumps can be used in a closed water to water ambient loop, kept within operating parameters by a primary plant technology such as an air source heat pump or a gas boiler.

4. Ground source or geothermal heat pumps (GSHP) take advantage of thermal energy stored underground, transferring heat in a similar manner to air source heat pumps. Due to the constant temperature of the ground, they offer much more efficient operation, however installation is pricier and more complicated due to the need for excavation and installation of underground piping.


There are two common types of GSHP:


1. Closed loop horizontal system or vertical system

  • A heat exchange fluid is circulated through pipes laid in trenches in the ground

  • Less efficient than an open loop system so more boreholes are required (often by a factor of around 40)

  • Generally, less cost effective than open loop systems – but up-front installation and design costs, are less.

2. Open loop system

  • Groundwater or surface water is extracted from and returned to a suitable body of water (aquifer below the site for groundwater, river, or lake for surface water)

  • Output is dependent on how much water can be extracted

  • More efficient than closed loop systems, so fewer boreholes are needed

  • Generally, more cost effective than a closed loop system

  • Can use cooling effect of groundwater without running a heat pump in the summer.


Advantages & Disadvantages




Heat Pump market: Technology movement analysis, 2018 & 2025


On the basis of technology, the heat pump market has been segmented into air source, water source, and ground source. The air source heat pump segment expected to dominate the market. Geothermal heat pumps expected to grow significantly over the forecast period owing to the advantage of stable temperature of its geothermal subsoil heat source.


Conclusions


One of the most important design choices in a commercial building is HVAC configuration, since this system represents a significant portion of ownership costs in the long term. U.S. Energy Information Administration, commercial buildings consumed 7 quadrillion BTU’s of energy. Further, HVAC accounts for 44% of the commercial building energy demand. Building layout is an important consideration: low-height facilities with ample rooftop areas tend to favor packaged rooftop units with VAV systems, while multi-story buildings tend to favor the use of chillers or water-source heat pumps.

Of course, there are viable energy efficiency enhancements that can be deployed in all cases. Modulating the speed of compressors, pumps and fans is more energy-efficient than cycling these pieces of equipment on and off, and it also contributes towards a longer service life and reduced maintenance expenses.

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