Energy Efficiency Specialists
Solar and Geothermal Technicians
Serving The Industry
SYSTEM DESIGN CONSIDERATIONS: FUEL SOURCES
The choice of fuel is not always an option. Availability generally dictates the source. All fossil fuels are subject to changing prices. This makes our investmestment on return and RET screen (payback) models vague. It would be our desire to see the public try and prioritize the choice of fuel that has the least amount of impact to our environment. By doing this they will benefit by the reduced operating cost. All new homes should consider alternative fuels as a secondary source. Many times we can reduce the cost of the primary source by doing this. Solar is free! Geo-Exchange is 300% efficient. When we combine these two systems we can multiply these efficiencies by three times. 900% What’s that all about?
People want to achieve different goals in choosing a heating system design. Some people prioritize financial benefits and reduced operating cost. Some people want to reduce their carbon footprint and do their part in reducing green house gas emissions. Other people prioritize their level of comfort. We seek to achieve all these benefits with every application.
This graph shows the relationship with the systems fuel source and the related impact the source has on our environment. It is important to note that cost of operation for a system does not reflect a reduction in greenhouse gas emissions. This graph indicates that an electrically sourced time of use system that is designed to provide low operating cost, actually has the highest negative impact on our environment.
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Convection:
Convection refers to the form of distribution that a system uses to transfer the heat from the source, into the building envelope.
Most convectors will operate at different temperature levels. In the past fuel efficiency was not prioritized. System designs incorporated higher operating temperatures and fewer convectors. Today’s designs often incorporate more convectors and lower operating temperatures. Lower operating temperatures result in load reductions from the source.
The lower the operating temperature -The more efficient the system will be.
Average convector operating temperatures:
- In and On Floor “tubing grids” (properly designed) 90-120 degrees F
- In and On Floor “tubing grids” (poorly designed) 120-140 degrees F
- Cast Iron Radiators 120-160 degrees F
- Cast Iron Baseboard 120-160 degrees F
- Steel Panel Radiators 140-160 degrees F
- Recessed and Flush Mounted – copper tube & aluminum 160-180 degrees F
- Steel Baseboard - copper tube & aluminum fin 160-180 degrees F
THE SOURCE “PRIMAREY”
We refer to the primary heat source as the stable source to a system. Many of the systems that are on the market are subject to conditions that can affect their production. For example: a solar system could never be considered a “primary” source. Regardless of the site conditions, there are times that we will have two or more cloudy days in a row. This will prevent solar production for that period of time. Most alternative fuel systems require a “primary” back up source of one form or another. This includes most forms of heat pumps. This does not imply that the primary source, when blended with another system is the main source of production. Most of the combined systems only utilize the “primary” system on a limited basis.
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VERTICAL TUBE STEEL BOILERS
VERTICAL TUBE STEEL BOILERS: These boilers are the most affordable boilers on the market today. You can have a replacement model installed for an average price range of three to four thousand dollars. There is moderate heat transfer from the source of the energy. The flue gases travel through the vertical tubes, slowed down by baffles, and then is extinguished into the flu pipe and out to the atmosphere by way of the chimney.
They have to operate at higher than (often) required temperatures. This is to insure that all the fuel by- products are burnt and dissolved into the atmosphere. The steel constructed heat exchangers will rot out if these boilers are run at reduced temperatures. They also are designed to maintain a minimal operating temperature. This is mainly due to their tank less hot water coils. The stand by loss is high and they have to fire regularly due to their limited insulation. The biggest benefit in this boiler is the cost. If these boilers are coupled with a properly designed baseboard or wall radiator (high temperature) system and the home has a tight building envelope, they should be more than sufficient for the home owner. If these conditions do not exist than we would advise the home owner to do some homework and make a better choice.
HORIZONTAL TUBE STEEL BOILERS: These boilers seem to be a little more efficient due to the Horizontal tube design. They do suffer from most of the same characteristics as the vertical tube cousin.
We refer to these as low efficiency boilers.
Boiler descriptions can be long and boring. Next to the addition of an alternative fuel source, they play the biggest part in allowing us to reduce fuel consumption. It is roughly 50% cheaper to make improvements to the boiler, than it would be to over compensate a poor boiler design by adding an alternative energy. We can improve a systems efficiency level by 20-30% by installing the right boiler to suit the application. This is why it is important to understand boiler design and related items.
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SINGLE PASS CAST IRON BOILERS:
These boilers are constructed by combining individual sections together to complete a single shell. The number of sections used will dictate the size and output required. The section design incorporates a cast iron pin area that is located where the sections come together. This area is the flu passageway. The pins are used in place of baffles to slow the travel of flu gases down and allow for the heat transfer into the heat exchanger. These boilers have a higher level of construction than their steel counterparts.
Most are still made from “sand poured” cast iron molds. This makes the cast iron hard and brittle. They are designed to maintain higher operating temperatures. This is partly for the prevention of temperature shifts which can crack the cast iron. They are subject to thermal stress conditions and can be difficult to clean. We refer to these as mid efficiency boilers.
A good way to indicate the efficiency level of your existing boiler is to have the stack temperature checked. These temperatures are checked where the flu gases exit the boiler, and just before the draft regulator. Boiler stack temperatures can range from 300 degrees Fahrenheit to ranges of 600 degrees Fahrenheit. (These are averages / we have seen temperatures above and below these ranges) The stack temperature will indicate the performance level of the boilers heat exchanger. A boiler with a stack temperature of 300 degrees is extracting twice as much heat from the source as a boiler with a stack temperature of 600 degrees. Does this mean that the lower temperature boiler is twice as efficient as the higher temperature boiler? Steel boilers have the highest stack temperatures. Single pass cast iron comes in second and three pass boilers have the lowest stack temperatures.
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THREE PASS CAST IRON BOILERS:
These boilers are the best dollar to dollar boilers in today’s market. There are a few models that can exceed the three pass performance levels. The extra cost and complexity of these models do not relate to the average person. These boilers use a silicone injection method for the production of their sections. This gives these boilers a great advantage over the competition. They can operate at low operating temperatures and will not suffer the affects of thermal stress or shock. The three pass design maximizes the extraction of flu gas temperatures through the heat exchanger. The features that we can incorporate due to the construction and quality of these are to numerous to note. The bottom line is that these boilers have all the required benefits to allow us to maximize the system efficiencies. These are high efficiency models.
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ELECTRIC BOILERS:
These boilers are ideal for providing a heat source for a low temperature in floor application. When used for this application they can be very efficient. They do take a long time to heat slabs initially. When the slab is up to a minimum temperature, they will heat a slab efficiently. Remember most electrical appliances operate at 100% efficient. This means that we achieve a 1 to1 production level for the fuel source. For every kilowatt of power consumed we will achieve the equal amount of energy produced. They do lag in recovery rates and are not ideal for high temperature system designs or domestic hot water heat exchangers. Set back features should be carefully regulated. It is easy to defeat the benefits of set back with an electric boiler.
We like to use electric boilers as the primary source to many of our solar designs. This practice applies mainly to new applications. The older systems are not usually compatible to the use of this product. These are also a good secondary (Back up) source for many other systems.
It is important to remember that electrically heated boilers and tanks have a more negative impact on our environment than any other source. This applies to time of use storage designs. The source of our electricity always originates at the power plant. Our power plants use dirty energy as its main fuel source. It is up to us as the consumer to reduce our loads. If we can reduce our reliance on the “grid” we will all benefit.
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HEAT PUMPS: GEO THERMAL
Their are many forms of heat pumps. These products have the highest efficiency rates of all grid connected appliances. We focus our designs around the water to water units. These units have the highest efficiency rates of all heat pumps models. The units above all incorporate three basic functions. They produce hot water space heating, hot air space heating and air conditioning if desired. They have a feature that will assist in the domestic hot water production, this only occurs when the unit is running.
The other model we use has water to water capabilities only. These heat pumps have an efficiency rating of 300%. For every kilowatt of power consumed we get three kilowatts of energy in production or a 3 to1 ratio. These units use three basic methods of extraction. A closed loop circuit is used to create the ground exchanger. This ground exchanger is sized to meet the design parameters. The ground exchanger if filled with antifreeze and circulating pumps move the fluid through the heat pumps exchanger for the extraction process.
Another method is a vertical bore hole application. This method is used in areas that have restricted availability for the horizontal loop design. We use drilled bore holes to accomplish the ground exchange parameters in a limited area. The bore holes are filled with a heat transfer medium after the lines are installed. This method can be expensive and is avoided when possible. The third method is called a pump and dump application. Water is pumped from a well, run through the heat exchanger and dumped back into another well or a drainage ditch. This method requires a well that has a large recovery rate and volumes. This is not an application to be used when the water source has to be paid for.
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Geo- exchange systems are ideal for low temperature designs. We are limited to supply temperatures in the 120 degree f. range. The domestic hot water usually requires the utilization of an electric buffer tank. When we combine these systems with solar, we can achieve fuel reduction that can not be matched by any other system design. The description provided refers to the most common and basic applications only. There are too many system features and design applications to list them all.
Solar:
A solar designed system is without a doubt the best way to reduce the operating cost to any heating system that uses hot water as its distribution fluid. Depending on the system and the budget, we can achieve minimal savings of 40% and above.
There are many products on the market and you have to do your research to make the right component choices.
The savings in using a solar design for hot water only is a hard sell. The actual savings you can achieve with a solar hot water “pre-heat” system amounts to an average of $ 111.00 per year/ per person. That is an average given by Conserve Nova Scotia. Of the total fuel consumed in a home 17-23% is used for the production of hot water. With the addition of solar, we can reduce that percentage by 70%. The average cost to have a “properly” designed system installed for a two person household averages between 6-8 thousand dollars. If a home has more occupants or has a higher than 159 liter per day / per person load, the size and cost of the system design increases accordingly.
We have prioritized our designs to be compatible to space heating. Once we establish space heating, we achieve additional 40% annual deductions. The total saving we can achieve with our standard designs will be 55%. This is without addressing any other items which may be related to the existing heating system. The size and specifications of all our components are relevant to the addition of space heating at some point.
Because our designs prioritize space heating, we have chosen to use evacuated tube collectors. Regardless of the claims made by all others, the evacuated tube collectors have the lowest heat lost factor. They produce the same amount of heat in July when its 72 degrees Fahrenheit as they do in January when its 10 degrees Fahrenheit. The heat loss related to an evacuated tube collector is only relevant to the insulation and sleeving methods of the feed lines or line kit. Their production levels are higher when we experience diffused radiation levels such as cloud layering and snow.
The main condition that affects their production levels is the shortage of sunlight. We experience this in the winter months and it affects all collector designs. The evacuated tube collectors require half the mounting area as a flat plate collector and produce about twice as much energy as a flat plate. To be fair, you can on average pay twice as much for an evacuated tube collector as you would to purchase a flat plate collector at the same level of quality. Doing the research will validate all these facts.
The key to achieving the maximum benefits from your solar design is in the installation. To provide a solar hot water pre-heat system is simple. The installation can be achieved by any person with a good mechanical background.
To provide the blending of a solar system to a new or existing heating system requires a skill set that can only be achieved by a licensed professional. The installer has to have a wide range of knowledge in many areas. The end result must be a single system that is derived from two separate systems. They must each work in harmony with each other and prioritize the benefits from the cheaper source. This requires extensive control strategy and hydronic system design knowledge.
The re-emergence of solar in our industry has brought forth many product suppliers,
All the product lines are appropriate for the right application. If the application requires a design that has to be done on a small budget, Solar may not be the system for you. There are systems that can be installed for smaller budgets: these systems often come with on foreseen issues. It would be our advice to postpone the solar installation until budget permits. Make the preparations, if necessary. Poor installations will only result in a negative public impression towards the technology.
Solar technologies have a proven history in the global community. The cost of these technologies can be high. The benefits to a properly installed system are unrivaled.
Check product warranties, Installers credentials or licenses and insure that you achieve the related grants and rebates.
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The item described up to this point should identify the most common fuel sources, forms of convection and heat sources in our local area. There are many items and products that we do not mention, it is not our intention to cover items that are not relevant to the public as a whole. We would hope interested customers will review the provided details and gain a better understanding of the items that apply to their situation.
All projects will have to take their conditions, application and budget into consideration to make the appropriate choices.
The following items will cover issues and opinions that you may or may not want to review. We are making note of some items that are not always relevant to a person’s application. It may make interesting reading to some, the facts are put forth for applications that will require specific knowledge or details.
Building Envelope: Although we do not repair building envelope issues, it should be noted that a homes building envelope will directly affect the efficiency levels related to any heating system design. Many times is it a better investment for a customer to repair their building envelope. This will improve the comfort levels in a home, improve system efficiencies and reduce operating cost. The best way to determine the condition of your building envelope is to have an energy audit. This also makes you eligible to grants in improvements. This applies to older homes only.
System Maintenance: All the performance levels related to a heating system rely on one key feature. The ability and efficiency of heat transfer. This applies when we transfer heat from the fuel source into the heat transfer fluid (water). This also applies when we transfer heat from our convectors into the home.
The fuel sources we use are generally referred to as “dirty energy” as opposed to “clean energy”. They are called dirty energy because they leave behind fuel by-products and deposits. These deposits gather on the surface of the appliances heat exchanger and obstruct the heat transfer of the flue gases. This soot and the related deposits have to be removed at least once a year. Clearances to the cleanout ports and draft hoods have to be accessible and in decent condition. A proper boiler cleaning can improve efficiencies dramatically. Most fuel providers will facilitate this service.
Convectors rely on a natural air current to travel across their fins and distribute the heat into a desired area. If furniture or draperies block this air flow they will not produce properly. The fin type convectors will accumulate large amounts of dust and dirt from a home without the knowledge of a homeowner. A handy man can remove the covers and vacuum out the radiation. If the sensitive fins are bent a fin comb can be obtained and the bent fins can be easily straightened. This can be done very cheaply and will bring the convector back to its original performance levels.
Most other maintenance items relate to licensed professionals. It would be our advice to have your plumber or heating technician change and flush the fluids in your system every two years. This will keep the fluids from becoming to acidic. All main components should be serviced and tested at the same time. Expansion tanks should be drained and make up valves replaced.
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Time of use applications: Many so called experts advocate time of use methods to reduce operating cost related to certain system designs. We do not! The most common method in applying this design is, a home owner has a time of use meter installed for their home. This meter allows the home owner to purchase their electricity at a reduced rate, during off peak schedules. The idea is to use the cheaper energy cost to heat a medium (usually a concrete slab) for storage and than distribute the stored energy into the home when the rates are higher. This will save in operational costs.
The problems we have with this design are: the loads required from the grid will quite often exceed the loads that the home may require the following day. We indirectly enlarge our carbon footprint by way of the extra CO2 emissions expelled at the power plant. We will use the same energy to heat the home regardless of the cost. It is very difficult to regulate an ambient air temperature .These designs will often lead to over or under heating of the living space. The only time this design works well is on a commercial building that maintains a load demand “constant”. This refers to a building that will not experience shifts in occupancy, external heat sources and many other factors. The idea is to satisfy the minimal load demands at an off peak rate. We then allow for changes in the buildings environment as they occur. This minimizes the buildings reliance to the grid.
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