The Return of Hydronic Heating and Cooling to Small and Medium Size Buildings
The Return of Hydronic Heating and Cooling in Small to Medium Size Buildings
In 1902, Willis Carrier invented the first air conditioner based on Carnot cycle and to today’s models, this discovery was driven by the need for cooling in certain manufacturing processes. Working with the Sackett-Wilhelms Lithographing and Publishing Co., who needed an efficient way to cool paper during printing, Carrier invented a machine that blew air over cold coils to produce the cooling effect. The machine de-humidified and cooled the air so paper would stay smooth and the ink fresh. This machine had the ability to cool air significantly and lower humidity levels by nearly 55 percent.
Since then demand for air conditioning and heating grew up steadily till the 1970s where Central HVAC systems were implemented in most commercial buildings in large North American cities, and many air conditioning companies popped up to help meet the demand.
Till the 1980s, primarily heating/cooling distribution fluids was water (or a water-based mixture) since unlike refrigerant, water can be transported long distances without involving a large amount of friction losses in pipes. Also control technology was not as advanced as today (IoT, digital control, etc...), water in its liquid phase (suitable for the operating temperatures/pressures conditions of most commercial HVAC systems) presented a simple, easy and affordable controllable fluid.
Despite the many advantages of hydronic cooling and heating systems, they were too costly for medium to small sizes commercial buildings and they required heavy maintenance for steel pipes, cooling towers chillers, chemical treatment, etc.….
1982 The invasion of North American Market by Japanese VRV (Variable Air Volume) Technology
In 1982, Daikin launched the new VRV (variable refrigerant volume) technology addressing the high cost and inefficiency of hydronic cooling and heating systems in small to medium sizes buildings. In such buildings, cooling/heating energy needs to be transported to relatively shorter distances than in large commercial/institutional buildings. Since 1986 (the time VRV technology was introduced to the North American Market) the VRV technology gradually took over hydronic cooling and heating in small to mid-sized buildings in the united states and Canada. This technology offered a higher energy efficient heat/cooling production unit since compressors was running on variable speed inverter which allowed to modulate the capacity of the equipment based on demand. that was no possible with traditional single or multiple stages heating and cooling equipment.
Cost of distributing/transporting energy versus producing it
- In the early 2000s, Daikin (Japan) and other Japanese and Chinese heat pump manufacturer started producing Air to Water Heat pump having VRV/VRF technology. Other manufacturer in Europe started producing larger capacities air cooled chillers that can run in both cooling and heating modes. This new technology combined the best of VRV/VRF technology and traditional hydronic cooling and heating system.
VRV/VRF technology was extremely inefficient when distances between Heat Pump and connected indoor units are high since refrigerant has a much higher friction loss ratio that water. Also published VRV machines performances did not match real performance in these cases
As shown in the below graph, the cost of distributing energy can be quite relatively high compared to the cost of producing it. Refrigerant is the worst and hydronic is the best when distances between equipment producing energy (Heat Pump, Chiller, Roof Top, etc...) and equipment distributing it (Fan Coil Unit, Air Handling Unit, infloor heating loop, etc...) exceeds 100 ft.
Graph Source: Hydronics Industry Alliance
Graph Source: Hydronics Industry Alliance
Why is there such a large difference between the energy consumption of a hydronic system in a commercial building vs. it’s competitor’s, air and refrigerant distribution systems??
The answer lies in the distribution or pumping energy and the way AHRI ratings of equipment are published: First: Equipment Manufacturers do not take into account the cost of distributing energy in their published equipment ratings (COP, HSPF, EER, etc...), Second: In an air system almost half of the energy consumption is pumping energy (Large fan energy), Third: In a hydronic radiant cooling or chilled beam system the pumping energy is much smaller, closer to only 20% of the total energy consumption (Most efficient system is geothermal/Thermal Solar generation and radiant cooling or chilled beam distribution).
Smart, Affordable and Efficient Hydronic Cooling and Heating Design Example
Solar Thermal as a primary heat source
The above design example combines Solar Thermal Energy (generated by our SRCC Certified Vacuum Tube Solar Collectors), Combination Buffer and Indirect water tanks (as a thermal storage and exchange hub), Air to Water Heat Pump (as a secondary source of heat as well as electric or natural gas boilers (whenever necessary) and other heat and cool distribution equipment (such as infloor heat loops, Hydronic Fan coil Units, Pool Heat Exchangers (for dumping excess heat in the summer) etc...
Hot Water Distribution network is designed in a way that return is always pre-heated with solar thermal energy before any other source of make-up heat whether heat pump, or boiler. Advanced Control system will prevent other connected heat sources to turn on as long as there is enough solar radiation to satisfy the heating demand.
Air to Water Heat Pump and/or Electric or Gas Boiler as a make-up heat source
The Air to Water Pump is a revolution in heat pump technology that remains unsurpassed in terms of cost and performance. Designed with a mission to make it the most efficient cold climate heat pump on the market at a price point of ½ of a traditional geothermal heat pump.
This was done without any sacrifices to quality. Industry leading parts were mandated in the design of this unit.
Hydro Solar Air to Water Heat Pumps can work in Canadian Winter for outdoor temperatures as low as -22.6 degree Celsius (-8.68 degree Fahrenheit) and can provide hot water at temperatures as high as 55 degree Celsius (131 degree Fahrenheit). The produced hot water can be used for space heating, domestic hot water heating, Hot Tub or SPA heating and many other heating process applications.
Annual Savings, Performance, Thermal Comfort and Long Term Benefits
Since Air to Water Heat Pump can provide hot Water for Space heating and Domestic Hot Water heating (both in Winter and Summer Time), the average annual coefficient of performance for a typical Canadian Home is 2.3 (without taking into account the heat generated by the solar panels). That means that every purchased KWh from utility company will provide the equivalent of 2.3 KWh of Heating and Cooling Energy. Air to Water Heat pump will switch into heating mode in summer when there is no cooling demand. Conventional Air to Air heat pump goes off in the absence of cooling demand in summer.
Comparing Air to Water Heat Pump to Water to Water Geothermal Heat Pump that has an average Coefficient of Performance of 3, it's 23% less efficient than a geothermal heat pump but it's way less expensive. a geothermal heat pump will cost the same as an air to water heat pump, but it will require a closed loop geothermal well that will cost between 12-15 K$.
Most Geothermal Heat Pumps can supply hot water at 105-110 degree Fahrenheit, which make them little useful for preheating domestic hot water (especially in summer time). However some come with desuperheater that can be used for domestic hot water preheating. Desuperheater can be used in heating mode only making it unuseful in summer time.