Energy Design Resources

Today's useful link:

http://www.energydesignresources.com/ is as close to 'the website I think should exist' for building owners and designers as I've found so far. It seems to have a collection of excellent case studies and tools.

Included on it are lots of resources for energy simulators, including a form to provide to chiller manufacturers to get standard data from them for simulation purposes.

Heat Pumps, Carbon Emmissions, and Carbon Dioxide: a Love Story.

I love heat pumps. The refrigeration cycle is an elegant and beautiful thermodynamics hack: by manipulating the temperature and pressure of a gas/liquid phase changing fluid, heat can be forced to move from a cold space to a warmer one. A neat trick on it's own, but better is the fact that the energy required to drive this process is significantly less than the energy that is actually moved - by a ratio of up to 6:1.

Best is the fact that the energy used to drive the cycle (which turns into heat via friction and ends up being picked up by the phase change fluid) is itself transferred to the high temperature zone. So in contrast to a fossil fuel heater, where 81% - 97% (at the very most) of the energy available in the fuel is transferred to the heated space, a heat pump moves between 200%-400% more energy than it uses in electricity.

However, heat pumps use 'freons' - the outlawed CFCs like R22, and the new HCFCs like R410A or R404A -- and these gases are expensive, were ozone depleting, and cause climate change. Furthermore, commercial HCFC heat pumps have historically been limited to outputs of 55C - considered due to bacterial growth dangers to be to low for domestic hot water use.

However, there is good news: one of the up and coming heroes of the refrigerant world is the world's leading climate changing gas.

Carbon dioxide (CO2) in the atmosphere causes climate change, and it is released in large volumes due to our civilization's fossil fuel addition. It's important to remember that carbon dioxide emissions resulting from disruption of natural carbon sinks is harmful to the planet's atmospheric carbon dioxide levels, but in previously occurring quantities of atmospheric CO2 (prior to about 200 years ago) this life-giving gas formed (and still forms) the building block plants use, in combination with water and sunlight, to grow.

CFC refrigerants, on the other hand, are synthetic chemicals with no origin or purpose in nature. I'm not intrinsically opposed to such chemicals unless they have negative properties - but CFCs, and HCFCs, the environmentally preferable replacements which do not cause ozone layer depletion - cause global warming at a rate 1500 - 4100 times the rate of an equivalent volume of CO2. And because refrigeration cycles require that the CFCs function in a high pressure environment and in a cost-effective piping system, even factory sealed systems can lose their refrigerant charge over time. In large grocery refrigeration systems, leakage rates of 5%-15% are not uncommon.

This environmental consideration, along with the very high cost of HCFC gas - is driving a current industry quest for cost effective refrigeration solutions utilizing natural refrigerants - that is, non-synthetic, naturally occurring chemicals which have phase changes from gas to liquid at temperatures and pressures suitable for food refrigeration or space conditioning.

Ironically enough, CO2, the 'problem' greenhouse gas, turns out to be a fantastic refrigerant. Here are some of the best features about CO2 refrigeration systems:

• low material costs in comparison to HCFCs, due to a high heat of vaporization, which allows lower mass flow rates through the system, and smaller tubing.
• the phase change properties of CO2 are such that much hotter condensing temperatures can be achieved in CO2 systems: products available in the marketplace today can heat water to 60C - 90C, while still operating with a coefficient of performance of up to 4.
• in some systems, this high output temperature can be created concurrently with very low evaporation temperatures; in fact, COPs increase with higher temperature differences between the low and high sides of the system. This is very unusual and creates opportunities for heat pumps where they would typically be unable to perform.
• very inexpensive: CO2 costs between .80c - $2.00/lb, versus $22-$30/lb for HCFCs.
• available: CO2 is used in the food industry to carbonize fountain drinks; easily purchased in large quantities anywhere in North America where fast food can be found.
  
  Japan's in this secret. Over the last 10 years, over 1.5 million 'EcoCute' heat pump domestic hot water heaters have been sold to homes throughout the country. These units cost 66% less to operate than an electric water heater. More information can be found at http://en.wikipedia.org/wiki/EcoCute.
  
  The only caveat to this love-in for heat pumps is that, depending on what electrical grid the heat pump is supplied by, the overall climate change impact of it's operation will change dramatically - and isn't always a win over a natural gas appliance.
  
  In Alberta, Canada, most electricity is generated by burning fossil fuels like natural gas in remote power plants to generate heat, and produce steam. This steam runs a turbine, which generates electricity (30-45% efficient process). This electricity is run through high voltage wires (7-8% line losses), through several step down transformers (each of which has 1-5% losses). Even with a COP of 3, it's probably better just generate the heat on site (3%-20% losses) than to bother with this.
  
  However, for many other grids, such as next door neighbour British Columbia, much of the electrical generation is sources from hydro, wind, and nuclear power. Without fossil fuel origins, there are only secondary environmental impact greenhouse gas emissions (i.e. methane from flooded lands for hydro) and line losses. The use of electricity to pull heat from surroundings and use it effectively makes sense for these areas, and supports the development of clean alternative electricity sources.

Building Benchmarking: getting started is the hardest part.

'Benchmarking' is the only way that organizations or individuals trying to measure the energy savings their hard won retrofits or new energy efficient buildings have created, and demonstrate them to a larger world.

This important exercise can also help demonstrate to stakeholders how the organizations facilities are faring as compared to the competition's buildings, or even how buildings within a single organization compare to each other.

Over the long term, access to this information helps the facility manager develop an energy use awareness - an internal sense of how much energy makes sense for a given building to use, and how much money to expect to pay for energy in a poorly insulated rental or purchase property.

Energy labelling of buildings is one suggested way of creating this awareness. ASHRAE has created Building EQ, a program which would label buildings anywhere from net-zero energy to unsatisfactory, both as designed and as operated, and provide owners an easy means of comparing buildings to each other. ASHRAE's Fundamentals textbook, published every 4 years, also has a upper, median, and lower quartile energy performance data for a variety of building types.

Energy Star is much more established program that allows building owners to compare their buildings to all other buildings of their type registered in the program, and, solely on the basis of energy bills per square foot (adjusted for occupancy and certain other factors) learn where their building ranks. The top 25% of buildings rate as 'Energy STAR' rated. The wonderful thing about this program is that the target moves with the industry: as better buildings are built and registered, the standard moves and helps move your organization along with it to maintain certification.

Lawrence Berkeley National Labs also has a fabulous program, Energy IQ, wherein a large quantity of detailed energy data can be accessed and sorted or screened according to building vintage, exact occupancy type, and more. A larger range of building types are available in this program as compared to Energy Star's database.

In addition to benchmarking a building against other buildings, it's advisable and often fruitful to benchmark a building against itself. By choosing a reference year (if your building is that old, 1990 has the benefit of being the Kyoto treaty reference year) and continuing to benchmark your building against that one year, the effect of internal retrofits and occupant behavioural changes can be demonstrated in an easy to understand way.

When implementing occupant behaviour change campaigns, logging and providing to staff ongoing progress statements - especially if one building can be pitted against another -- can help foster healthy competition and a sense of pride in the achievements of the organization and of teams within it.

I hope that energy benchmarking becomes a part of your month-to-month energy management routine, and can provide an ongoing value with performance feedback and growth.

15 Minute Blog: Fan Efficiencies

Recently I had to select some small and some medium sized fans for a sustainable project.

The small fans were a breeze: it was a light commercial building, so I went with residential quality exhaust fans. I selected them from the Energy Star excel list of qualified fans:

http://downloads.energystar.gov/bi/qplist/vent_fan_prod_list.xls

These lists are available for all Energy Star certified equipment, and are great tools for selecting them: find a good performance index (for fans, I used CFM/watt) and then select one of the better performing, reputable manufacturers.

I put the CFM/watt effectiveness requirement right on the drawing, so that I would be guaranteed the performance I wanted from what was installed. I could also provide a good list of alternate suppliers who also meet the efficiency standard right from the Energy Star list.

The larger fans were much harder. I used a fan selection program from a major manufacturer to determine which kind of fan they sold would be in the right range for efficiency and price-point, given the parameters I needed, but the program listed a variety of different efficiencies, none quite as easy-to-understand as a CFM/watt. ASHRAE lists motor efficiency requirements, and BHP requirements, but these aren't typically provided by the equipment selection program. Without some calculations and work on my part, it was difficult to even tell if the selected fans met our standard minimum efficiency requirements. I'm not allergic to work, but if energy efficiency were considered as important as other performance indicators, our industry would have standardized ratings - the EER of the fan industry.

This problem is endemic in medium-sized HVAC products. Very small, consumer goods are being provided with clear information about operation, and are benefiting from good engineering practise to reduce energy use. Very large equipment is subject to rigorous examination by engineers for energy efficiency, and is the focus of large manufacturers for efficiency increases.

Medium sized equipment -- fans in the 400cfm - 5000cfm range, for example -- seem to be left behind by today's practises, even through the majority of Noth American commercial buildings are full of them.

Refrigeration in sub-arctic climates.

Food preservation in Canada has always been a bit of a 'hot' topic for me. We use energy to cool food in a climate that is often colder then the intended food preservation temperatures.

On a residential scale I've tried to design alternatives to the current system (packaged refrigerators that plug into the wall) but there is a certain elegance to the status quo. Here's why.

Most of the time in Canada it's cold. The refrigerator is a heat pump, and it takes heat from the inside of the refrigerator (where we don't want it) and puts it in the kitchen - in the wintertime, a place where we do want it. Although better heat pump efficiencies would be realized by placing the condenser coils outside, we would then be transferrring heat from inside the refrigerator (which, you'll remember, was first generated using the house's furnace for the purpose of heating the house) to outside the house.

Condenser cooling with outside ambient air would have much better efficiencies, of course, but the electricity isn't wasted by the compressor - it also heats the house. So maybe the status quo isn't so bad.

The system could be improved by rejecting to a water loop, instead: you could then move the heat more readily from behind the refrigerator to places it was really wanted.

Another way I see to improve upon this system is to directly circulate outside air into the refrigerator in the wintertime. This invokes concerns of air quality, pests exclusion, moisture control, and summertime air exclusion, but seems otherwise viable. Le'ts look at the issues:

1. Air Quality

Could be addressed by a HEPA filter or maybe something of lesser grade.

2. Pest Exclusion

Could be addressed by mesh, especially in combination with a HEPA filter.

3. Moisture Control

Due to the low temperatures and moisture removal by the evaporator coil, food withers in a residential frdge without protection anyway (the crisper or packaging.) It might be sufficient to warn owners to pay particular attention to tightly wrap food in the wintertime. Controls to only exchange air when required to lower box temperature will limit fan energy consumption and moisture loss.

4. Summertime Air Exclusion.

This would require a insulating damper with tight tolerances that is freeze-resistant, which might be the most expensive part of this system.

Ideally the entire system would operatate using a maximum 6" insulated duct to an outside wall, away from contaminated air (street/driveway) and should be billed as no more difficult to install then a laundry exhaust or range hood. The duct should contain two smaller exchange ducts, so that installation is very simple. An exterior wall grille designed to prevent short cycling or air would complete the package.

Perhaps, with sufficient design effort, a way could be devised to use the same duct to remove heat from the condenser from the house altogether in the summertime.

The problem is... could the cost (including installation labour, extra materials) be justified by the savings? Could operation be rendered sufficiently simple to accomodate the needs of consumers who rarely emply lint traps or change furnace filters?