Energy infrastructure and conservation methods are foundational to the creation of self-sufficient and self-propagating teacher/demonstration communities, villages, and cities to be built around the world. This page is an open source and free-shared guide to the hydronic systems setups to be implemented in the village models, the Duplicable City Center, and beyond. Once on the property, we will continue to evolve this page with additional implementation details, research, and systems development, installation, and maintenance specifics.
This page contains the following sections related to hydronic systems:
Hydronic heat transfer is the use of water as the heat-transfer medium in heating and cooling systems. Some of the oldest and most common examples are steam and hot-water radiators. Historically, in large-scale commercial buildings such as high-rise and campus facilities, a hydronic system may include both a chilled and a heated water loop that provides for both heating and air conditioning. Chillers and cooling towers are used separately or together as means to provide water cooling, while boilers heat water.
Water, being dense, transportable, and able to store heat-energy is near ideal for sharing heat around a building or dense community. In the case of One Community and the Duplicable City Center we will only use the heating qualities of the system to keep it, relatively, simple. While the oldest hydronic systems utilized steam radiators in separate zones (rooms) modern systems use hot water around 105 degrees F. The lower temperature of the water reduces the amount of heat that is lost to the environment. In our case we are not using a radiator per se, but a radiant floor that will disperse heat around the Duplicable City Center in times of cold weather.
Hydronic systems are more energy efficient than forced-air systems and they allow for the easy creation of zones so heat can be provided where needed and spared where not needed. They will also allow us to explore the process of transferring heat to water as a cooling option.
These systems are so effective that many larger cities have a district heating system that provides, through underground piping, publicly available hot water. This is essentially what we are doing through the use of point-of-use heaters and a continuously heated massive hot water tank to provide warm water to heaters that then only raise the temperature as much as is needed for the activity.
Ron Payne: Mechanical Engineer and HVAC / Thermal Designer
After the “landing party” has completed their site survey, identified the locations of all planned construction (specific for buildings to be built in the first five years, plus long-term general plan), begun working on the infrastructure, and completed and gained approval for all the initial building plans, the rest of the Pioneer Team will move onto the property. At this point the hydronic system starts to take shape. First the system will be very simple and relatively inefficient, but as energy saving measures are added the efficiencies will increase.
Here is the cost analysis for the complete system: (prices current as of 10/2014)
|Equipment Needed for this Phase
|Stiebel Eltron DHC-10-2, Tankless Water Heater
|Bell & Gosset Heat Exchanger
|Heat Exchanger, Plate and Frame, Max. BtuH 240,000 Water to Water Application
|Centrifugal Pump, Power Rating 20 HP
|Stiebel Eltron DHC3-1
|Electric DHC Series, 120 Volt, 3000 Watt Electric Tankless Water Heater
|Trane EXWE240 Heat Pump
|Water Source Heat Pump
|Electric Hot Water Boiler
|C2N363/480D C2N Series – Light Industrial Heaters
|Electric Hot Water Boiler
|C2N503/480D C2N Series – Light Industrial Heaters
|2 Inch White PVC Schedule 40 Pipe
|Uponor Radiant Flooring
|Pipe Insulation, Hinged with Self Sealing Lap
|Pipe for In-Ground Heat Exchange
|Hot Water Tank
|Norwesco 5000 Gallon Tank
|Johns Manville 11-Pack R-30 Fiberglass Insulation (48-in L X 24-in W X 10-1/4-in D)
|Misc. Valves, Elbows and Plumbing
|Estimation of various plumbing parts needed on the property to ensure safe operation based on piping length
During this time of rapid expansion on the property, hot water comes online using instantaneous heaters at first to raise the temp of groundwater that is pumped from the well to the units and the temperature is raised to a usable 105 degrees for the end use: makeshift showers and other domestic uses. Due to their small size these instantaneous (tankless) heaters will move where they are needed at first, but eventually find their more permanent places in the Duplicable City Center and shower domes of the Earthbag Village (Pod 1).
The second phase of this is the implementation of the hot water tank and the heat pump. The water tank will be insulated and installed in a relatively high point and nearby the heat pump will take in groundwater and chill it to heat the water cycling through the tank. The chilled water can be used for adhoc food preservation or other cooling duties before being dumped into ponds and other non-potable water uses. The tank will keep topped off by a simple float valve filling from ground water. The higher temperature which the tank can be kept the better, although high temperatures induce more losses. The instantaneous water heaters will be fed from this tank and “boost” the temperature up to usable levels. However, with the input temp higher the water heaters will produce their 105 degree water with less power usage.
Here are the hydronic systems action items for this phase:
By now, construction of the initial components of One Community are in full swing and we’re ready to bring on additional Pioneer team members to accelerate the pace of progress. Along with population increases we will see the demand for hot water increase. As the demand grows we leverage any advantages we can through increased energy efficiencies associated with a larger system and implementing some of the other energy reducing measures.
As development continues the need for hot water for uses other than showering and domestic uses comes into play. The most notable is the Duplicable City Center’s radiant floor heating. As this system comes online the electric boiler (perhaps with slave diesel generator at first) is piped into a loop that runs from the hot tank to the boiler (acting in the same way the smaller instantaneous water heaters do) to the flooring and back to the hot water tank. Ideally the spent water emerging from the flooring will run through the heat recovery hoods on their way back to the hot tank. The increased temperature at the hot tank will be boosted by the heat pump and returned to the boiler closer to the target temperature for the flooring. Because the electric boiler does not have to heat the water as much, the amount of energy decreases.
On the other side of the heat pump (the “cold” side) efforts will be made to extract energy from any source possible while keeping implementation inexpensive and flexibility high. To do this the chilled water can be used for refrigeration processes as before, but then run underground in an uninsulated pipe to take advantage of the geothermal heat properties (raising the temperature to groundwater) and then the newly warmed water will run through some passive systems like a heat exchanger from non-potable drain water and solar heat collectors. The warm water then enters the cold inlet side of the heat pump making the heat pump cycle more efficient.
This will be the hydronic system in its final form. Over the years parts will be exchanged out for more efficient models, and research will be done with the system, but overall this is the system that we believe will be the most useful to the property in the long-term.
Here are the hydronic systems action items for this phase:
They hydronics system for 50-100 people will be duplicated and expanded for the village models needed to house 100-400 people. The system above will supply sufficient needs for the Earthbag Village (Pod 1) that will be capable of housing 100-150 people. Based on what we learn from that, we’ll implement a similar system for the Straw Bale Village (Pod 2). The Duplicable City Center system will actually increase in efficiency as more people use it (due to reduced heating needs and increased heat recovery) and will not need to be increased or added to until we have more than 400 people consistently on the property.
We will open source and free-share here all the details of each additonal generation of hydronics system as we create and evolve them.
Heating and cooling of living spaces and water are two of the largest consumers of energy. One Community’s goal with open sourcing and free-sharing hydronic systems is to demonstrate the most sustainable and energy efficient methods for meeting living space and hot water needs. We are doing this here as part of our global change methodology for self-sufficient teacher/demonstration hubs and Highest Good energy contribution.
Q: How does the water get used?
The water is stored in a large tank and is drawn out, heated, and replaced by the heat pump constantly. The radiant flooring in the Duplicable City Center also draws water out as needed. Heaters then boost the water temperature to heat the Duplicable City Center and return it to the tank. This allows the waste heat used in the heating of the Duplicable City Center to be saved and used again.
Q: How was the system sized?
The largest user of the hot water system is the Duplicable City Center’s radiant floor system. From heat analysis of the domes we have found the amount of heat needed to keep the center warm on the coldest* day of the year and then calculated the temperature and flow rates needed to match that day’s heat needs. From there we added the amount of domestic hot water used around the property for things like showers and washing. The total flow of the system is enough to supply both these needs.
Q: How much water does the system use?
That is a harder question to answer. While the amount of water in the tank (5000 gallons) can be easily calculated, the amount of water in pipes, the boilers, and other components of the system are harder to calculate because we don’t yet know the specifics of where all the equipment will be located. One advantage to having a large (5000 gallon) hot water tank/reservoir, however, is that the system can store more energy for longer. This makes the system more rugged and able to deal with small failures without wasting too much energy while keeping the system working. Similar to actual mass, the added thermal mass of the extra water resists change in short term weather and mechanical defects better.
Q: Why not steam?
While there are many benefits to steam heating, the high temperatures in pipes create a higher incentive for heat loss through pipes and other devices to the outside. Since heat flux (the flow of heat energy) from a hot source to a cold is dictated by the temperature difference as well as the insulating properties of the barrier to that movement, the higher temperature of steam means that more energy is lost to the environment. To minimize this loss the water will be warmed as much as possible (80-95℉) and the remaining energy needed to heat the water to the useful temperature of 105℉ is added at the source where it is needed so minimum heat is lost in transit.
Q: Can you drink the water?
As of now almost the entire system is potable (meaning suitable for human consumption), however, as the cost for this ability is evaluated there may be a switch to non-potable solutions with more heat exchangers to transfer heat energy from non-potable to potable water.
Q: Why is it so complicated? Can’t you just heat water from the ground?
The answer for this comes from the definition of a BTU or British Thermal Unit. One BTU is the energy it takes to heat 1 pound of water 1 degree fahrenheit. A gallon of water weighs 8.33 lbs so one gallon takes 8.33 BTUs to heat up one degree. Given that groundwater at the site will probably be around 55℉ and our operating temperature is 105℉ that means that every gallon of water used would have to be heated 50℉. At 8.33 BTUs for every degree we heat our gallon of water that means that we need 416.5 BTUs just to make that gallon of water usable.
In a simple solution we would take cold water from the ground and heat it 50℉ before using and dumping the rest. With the amount of hot water being used, however, the energy costs would be astronomical: 57,477 BTUs per minute or 1.01 megawatts!
Q: How does the heat pump heat the water?
A heat pump takes heat from a source and delivers it to another. It does this by compressing (and therefore heating) a working vapor and allowing that heat to move into the side of the heat pump that is to be heated. After delivering as much heat as possible through heat exchangers the condensed vapor goes through a valve to the low pressure side of the loop. Because the pressure drops the temperature drops as well (see Boyle’s Law). If this temperature is then less than the source temperature, the newly cooled fluid absorbs heat and changes state to a gas (boils). Then that vapor enters the compressor and the cycle starts again. The effect is that the cold side gets colder and the hot side gets hotter.
The benefit is that the energy that it takes to heat and run the pump is less than what it would take to heat the hot side directly. This gives the heat pump an apparent efficiency over 100%. Here a graphic showing this:
Q: What about geothermal heating?
We are planning to use geothermal heating in our design. Geothermal heating means several things. However, in this context it means using the normal ground temperature as a stable thermal point from which to run a heat pump. In our case this is the cold side of the heat pump. Given that the ground temperature is around 55℉ for our location, a length of un-insulated pipe run below the frost line can absorb heat from this massive thermal reservoir. When the heat pump chills the water by transferring the heat where it is used, the chilled water is then run through this pipe and re-heated to 55℉ by the constant ground temp. The pipe returns to the cold source side and the process repeats. In effect we are using energy to chill the earth’s crust. However, since the earth is massive the result is infinitesimal.
For those also considering geothermal heating. Here is a graphic of the average groundwater temperatures in the US:
Q: What about solar water heating?
We will utilize this source as well. Solar heating is favorable because it is direct, simple, and easy to maintain. The downside is that it is not constant. Often when you need or want the heat the most (winter) is when there is the least amount of solar radiation. Still, using what solar energy is available is highly advantageous. Especially since it is so easy to create a passive solar water heater. The real issue is that the heat energy that we can capture is extremely small in the winter. However, as a tool to heat the cold source of the heat pump, event the small amount of energy available in the winter can be put to good use and translated through the heat pump into hotter water.
For those also considering solar water heating, here is a graphic showing solar radiation in the US. Due to weather and seasons creating variability in solar energy this will not be a primary source for us.