Excessive Air Conditioning Is Hot Topic In United States
Originally published on RMI Outlet.
By Craig Schiller
A recent New York Times article, “Enduring Summer’s Deep Freeze,” described a scenario we’re unfortunately all to familiar with in the summer: over-air-conditioned buildings. While a blast of cold air may provide welcomed relief from a triple-digit-temperature day as you walk into a convenience store, many office workers can attest that sitting in an over-air-conditioned space for long periods of time is less than comfortable (and can lead to decreased productivity and morale).
There is a fine line between a brief, refreshing, cool blast of air and prolonged exposure leaving individuals chilled enough to resort to individual space heaters or blankets in summer just to warm up. Bloomingdale’s has even started advertising “summer cashmere”—oxymoron that it is—to those of us who suffer from excessively cooled indoor environments: “from overactive ACs to seaside breeze, we’re really feeling our ultra-cozy cashmere.” This “blast the AC” strategy is rampant in the U.S. and has become part of our office and commercial culture. A recent Washington Post article highlights the excess of our cooling compared to the rest of the world: “While indoors, Europeans wear sweaters in winter, while American wear sweaters in summer.”
Let’s not diminish the importance of being comfortable, however, but rather simply discredit the concept of excessive air conditioning as the best mechanism to achieve comfort. In fact, multiple studies have proven that providing some cooling increases working productivity and happiness.
Some cool is good, but averages miss the mark
Not surprisingly, there is a mountain of research around air conditioning and the health, comfort, and well being of building occupants. People have a comfort range in which they maximize their productivity simply through the absence of discomfort (such as sweating or shivering). Also, at a building or societal level, the term comfort is used to describe the average levels for individuals. A recent article in Energy Manager Today points out that even industry organizations such as ASHRAE use an average of more than 1,000 subjects to create their thermal comfort standard.
As summer temperatures reach their highest points, the idea of dictating comfort as an “average” becomes increasingly polarizing, particularly between men and women. For example, how often have you seen two colleagues occupying the same workspace with the same temperature and one has a space heater under their desk? Ultimately, it is an individual’s personal comfort that is actually important, not the thermostat’s setting on the wall. As anyone working in an office can tell you, what is considered comfortable varies greatly from person to person.
Getting personal about individual perceived comfort
The U.S. building industry needs to break the incumbent standard of relying on energy-inefficient centralized heating and cooling systems to meet everyone’s comfort needs. Ironically, with our currently fossil-fueled grid, we are actually warming the planet by making our buildings cooler due to the 100 million tons of carbon dioxide the U.S. releases each year because of our obsession with cool indoor environments. In fact, air conditioners are so pervasive in the U.S that AC units consume about five percent of all the electricity nationally produced.
We should instead follow the logic behind the 80-20 rule by using central systems to get a building’s comfort “most of the way” generally and utilize individual heating and cooling controls to meet everyone’s comfort needs specifically. This approach allows comfort to be personalized to each occupant while saving energy by not over-conditioning a space. RMI will showcase this thermal comfort approach in our under-construction Innovation Center—a 15,610-square-foot office in Basalt, Colo.—with a pioneering approach to thermal comfort.
The six factors that influence thermal comfort
Set points commonly range from 70 to 76 degrees F in commercial buildings, but the Innovation Center will have an expanded range spanning 64 to 82 degrees F. Those six extra degrees on the high side, while seemingly insignificant, provide tremendous opportunities to save energy by avoiding excessive AC.
Just looking at these temperatures, people’s gut reactions are that they will be uncomfortable. However, temperature is just one factor controlling your comfort. Think of how much cooler you feel when the humidity is low or a fan blows on you. The absolute temperature may be high, but you can still perceive the temperature to be cooler. Six factors ultimately determine how humans feel in a space, and how our staff will specifically feel comfortable in the new office:
- Air velocity using ceiling fans and personal fans
- Air temperature through natural ventilation
- Surface temperature from cooling thermal mass in the floors and wall overnight
- Occupants’ activity level designing the space to be comfortable for all of the possible activities
- Humidity taking advantage of Colorado semi-arid climate
- Occupants’ clothing level encouraging occupants to dress comfortably
Conditioning people to feel comfortable through these variables proves far more efficient than conditioning the space those people occupy.
Bye, Bye, Air Conditioning
With this mentality, and through integrated design, our design team entirely eliminated a centralized cooling system from the new building. While focusing on all six variables is not seen in most buildings, it is actually based off an established approach using ASHRAE 55, a professional standard for thermal environment conditions focused on human occupancy. However, many owners and contractors perceive additional risk implementing this approach due to an over-simplified gut instinct after looking at the temperature ranges. Therefore, it is crucial to engage everyone from the occupants to designers and contractors up front so they understand and are comfortable looking at all six variables.
Chris McClurg, a senior associate at Rocky Mountain Institute who coordinated the thermal comfort strategy at the Innovation Center, believes this is the approach buildings will take in the future. She says: “Once the team is able to step away from the standard rules of thumb and gut checks by openly discussing the risks and benefits of this approach, they can focus on providing enhanced personal comfort where energy savings are almost a secondary benefit.”
Alternatives to Cranking the Cool
The Innovation Center will employ several personal comfort technologies, including a cutting-edge personal heating and cooling chair (imagine having an adjustable heated car seat as your own personal desk chair, but one that has fans to cool too!), which help eliminate mechanical systems. For example, a super-efficiency ceiling fan can provide the same cooling effect as an air conditioning system but at the fraction of the cost or energy. But why fan an entire area when you can provide air movement directly to an individual through personal fan? A room doesn’t need to be comfortable—people need to feel comfortable.
RMI will also utilize personal USB-powered fans to regulate airspeed directly to individuals, another important factor in warm weather. Accessories like radiant underfoot pads or heated mouse pads also help in the coldest weather. We’ll also encourage low-tech comfort solutions, such as inviting everyone, from staff to visitors, to dress seasonally appropriately and rely on old-fashioned common sense—and just plain fashion. There is no question that a critical mechanism to widely implement a “seasonal dress policy” is a national cultural a shift in business dress codes.
Staying Comfortable in the Coldest Climate Zone in the U.S.
In the new building, the only mechanical systems are for ventilation and localized backup heating equivalent to roughly 13 hairdryers. By accounting for all the thermal comfort variables, the building’s mechanical room was reduced by 200 square feet, compared to traditional buildings, because of the lack of additional equipment.
This is all made possible through passive, integrative design. The building is a passive, climatically responsive showcase for cold regions, highlighting proper orientation, a highly insulative envelope, exceptional daylighting, solar gain and shading strategies, natural ventilation, thermal mass, and nighttime flush.
With a predicted energy use intensity of just 17 kBtu per square foot, the Innovation Center will be the most-efficient building in the coldest climate zone in the U.S. (including solar PV, the building will be net zero, producing as much or more energy than it uses annually).
Opening Soon… Come for a Comfortable Visit
The Innovation Center will immediately be put to the test, opening this winter where average temperatures in Basalt range from 6 to 33 degrees F in the month of December. A crucial first step will be to train staff members on ways that occupant behavior will make or break our ambitious performance goals. And sure, the Innovation Center is being built in the Colorado Rockies at 7,000 feet elevation (ASHRAE Climate Zone 7), where heating is the primary concern rather than cooling. It doesn’t get as hot as a sweltering summer day in Dallas or Phoenix, but the same thermal comfort strategy principles apply for both heating and cooling.
The Innovation Center managed to eliminate our cooling system; other high-performance buildings in different climates have similarly eliminated their heating systems. While this is a small achievement, it is invaluable to achieve high performance or net-zero energy building statutes, both of which are rapidly-growing classifications. And most importantly, by providing the means for each occupant to be comfortable year round, employees and visitors of the Innovation Center will be healthier, happier, and more productive.
So if you do find yourself swinging through Aspen’s Roaring Fork Valley next summer, and you’re looking for a respite from a hot, sunny day in Colorado’s mountains, stop by and visit our new Innovation Center. Our comfortable staff will welcome you…
Image courtesy Shutterstock.
Reprinted with permission.
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It is good to remember that with renewable solar energy, wasting of energy is irrelevant because we have anyway huge overproduction of solar power on hot and sunny summer days.
Basically agree. What’s interesting is that if electricity were plentiful, cheap, and clean, people might even use it to heat their houses (someday), as at some point, despite its inefficiencies, it would be better than even oil/gas for that purpose.
A lot of homes built in the 1960s had all-electric heating.
I lived in one as a child in western Houston, TX.
This was back in the days that (some) utilities thought nuclear power would make electricity “too cheap to meter.”
I lived in one of those places with too cheap to meter nuclear energy and electric heating. $600 a month electricity bills!
You don’t have to go back to the 60s, necessarily–I replaced a dead oil furnace in the early 80s with electric baseboard heaters. That was in Ontario, which still has pretty cheap power (despite the worries of anti-wind zealots.) It was quite affordable (far more so than a new furnace, anyway.)
Of course, other than using a modicum of carbon-neutral combusted sources for a few applications, renewable energy generated electricity will eventually be the standard heating and cooling power complementing the ambient temperature to achieve the required level in our structures.
The much more ambitious, and currently impossible,task of determining and maintaining our globe at the optimum temperature conducive to long-term survival of our dense and vulnerable population will, ultimately, have to be attempted, I suspect sooner than we think. For that, electricity will not be enough.
Why are you so confident that electric heating, be it direct or through a heat pump. will come to dominate heating?
Biomass is still an extremely viable source of heat, especially if heat demand is large. An extra advantage is that it can be used twice: you generate process heat (for chemical or food processing plants, among other things) and then use the waste heat to heat buildings either via a district heating system or on-site. For larger installations, biomass also offers an attractive source of cooling through aborbtion cooling.
Oh, and then there’s solar thermal. Being a mature technology , it gets less attention than PV. However, installation rates are rising rapidly in the west (including in Germany, where solar PV continues to slump) and is close to universal in new buildings in China and other Asian countries.
I suppose simply because it is essentially simple and there will be such an abundance of electricity, something which cannot yet be envisaged.
You sound exactly like a nuclear power leaflet from the ’70s.
The thing is that both biomass and solar thermal technology are still advancing steadily, just as renewable electricity is.
And as for simplicity: what can be simpler than burning already overly abundant biomass?
There is a reason that very large customers like greenhouses, which are extremely conscious of their energy cost, are installing biomass burners (increasingly of the CHP kind for maximum profit), whereas electric heating of greenhouses is still unheard of expect in rare cases where deep geothermal is feasible.
Because sustainable biomass is not sufficient for heat and actually a waste in this field, we need green chemical feeedstock.
Efficiency plus heat pumps are the way to go for heating of buildings.
We’ve been heating our home with an electric heat pump since 2001 in the mid-west USA. Our electric rates are relatively low ($.128-.162/kWh) compared to some other regions, so it works well for us and it’s not that expensive with our moderately tight 1982 home. Solar electric and solar thermal (hot water), combined with a newer and more efficient air source heat pump, will drive down our electric use even more (50%) in the the next few years.
Our highest total electric bill last winter for the Jan.-Feb. period was app. $175 for our 2200 sf home. Total electric use was 1,305 kWh, with 5K of that for non heating purposes. We keep it at 70F during the day and 66F at night during the winter. The heat pump is HSPF 8.5 and 13 SEER and single stage scroll compressor. Last winter’s coldest nighttime temp. was around -6F, to give you an idea of our climate.
Thanks. That’s lower than I thought. Out of curiosity, what do you keep your thermostat set to in the winter?
Heat pumps have less capacity to quickly raise temps. during cold weather, so we just keep it at 70F from 8 AM to 9 PM. The compressor just hums along and runs a lot during sub freezing temps. and then occasionally goes into defrost mode. before coming back on. Register temps. are not hot like with natural gas heat (120F), but perfectly acceptable at around 82F-98F in sub freezing temps. There is also a setting to delay the blower coming on and lower the blower speed during heat pump cycle startup for comfort, and we use this, although it does reduces efficiency a little. This setting prevents the cool air blast that made people dislike heat pumps in the 70s and 80s.
We let it drop down to 66F for night sleeping and then raise it in stages early in the morning. 68F at 6 AM, 69F at 7 AM, and 70F at 8 AM. The heat pump itself also pre calculates all of this 90 minutes prior to any change in setting. Such thermostat settings prevent the backup electric resistance coil from coming on, although ours is turned off above 5F anyway. Most heat pumps can be adjusted in hidden menu settings, the instructions for which usually comes with the install manual. You can also pay the HVAC company $80 to come out and make such changes.
I should add that our 2200 sf home is a bi-level, so only the upper half of the lower 1,100 sf is above grade and maybe 1,320 sf is considered for heating and cooling load due to lower level temp. moderation. The same could be said for ranch homes with walkout basements that are living spaces.
Natural gas customers are being penalized by our utility right now, and there is more to come in the next few years. This penalty is called the fixed distribution charge. It’s $12.50/month right now and will rise to $23/month by 2021, regardless of how much NG you use. You get hammered in the summer if you only use NG for space heating, or just moderately pounded if you use NG for space heating and water heating. If you also use NG for the stove and the clothes dryer, then it’s not so bad, that is until NG price go up again to $8+ per unit. It will happen, it just a matter of when. The rest of the world already knows about high NG prices, but we seem to have forgotten.
Some customers with only NG space heating have asked about turning off NG service during the spring/summer/fall, but the $100+ utility fee per run makes it uneconomical.
Fixed distribution fee increases are to replace old NG distribution pipes rotting in the ground, so it’s necessary, although there should be a 3rd party that decides on such preventative upgrades. I’m sure there is. Look for such fees coming to your area soon if you live in an older part of the USA.
The solution for avoiding duplicate fixed fees is to go all electric, hopefully renewable sourced, for everything.
But not much on winter evenings. I share your prediction, but since there are always some non-renewable resources involved, waste is still a vice and frugality a virtue. Consider also that the most optimistic projections are for 100% renewable energy by 2050. The RMI building will be saving carbon emissions for 35 years.
I think that we can go to 100 % much sooner than by 2050. Perhaps by 2035.
I guess that the biggest obstacle is how fast we can get rid off the stranded assets of fossil fuel industry. But any carbon tax and/or import tariffs will force fossil energy industry into quick bankruptcy.
There is virtuous cycle or death spiral – Depending on your view. The more we install windmills and solar roofs and distributed batteries in smart grid, the harder it is for other electricity generators to survive. And as they fall, the more we need to install windmills, to cover the gap that was left remaining from the lost fossil energy industry.
Synthetic fuel production is more than adequate long term storage solution for wind and solar. And synthetic fuel is very close to parity with fossil oil based transportation fuels.
No, that’s bullshit, I hate a 72 F room in the summer, it really doesn’t feel right at all.
there are different perspective. Here in Finland, we have 72 F rooms also in Winter. Where as the rest of the World is shivering due to inadequate thermal insulation.
So far in 2015 Solar has supplied 0.63% of our total electricity supply (its actually a bit more because the EIA number doesn’t include rooftop solar The effect you describe will become significant when and if solar is ever producing somewhere around 70%+ of our total energy needs. I think you’re putting the cart before the horse.
no, it takes mere few years to ramp up solar and wind production. In Germany Wind and Solar is producing about 20 % from electricity demand and this was accomplished in mere decade. As Solar and Wind resource is more favorable in US, by 2025, about 40 % of electricity could be produced from wind and solar. And this is big enough market share for wind and solar that it forces all the rest of power generators into bankruptcy and therefore the transition from 40 % to 100 % will take perhaps seven years more. So, my estimate is that in United States is forced to 100 % wind and solar energy by 2035.
People usually underappreciate how fast wind and solar energy production can be scaled up. But it can be as fast as iPhone revolution was. That is, we have now fully matured smartphone infrastructure about one decade after the first modern smartphone!
If power is generated from solar, heat from the power plant will be reduced, which in turn should reduce AC requirement (ofcourse it will take another 100 years to reduce just one degree celsius).
Which again will make climate cooler so you too will use less AC.
Plant some shade giving trees in tandem with reducing AC world will be lot cooler.
Good article, but I don’t see abandoning A/C in Houston,Texas any time soon.
Generally women like us suffer when working in corporate offices. The airconditioner settings were designed for the comfort of average men, and it is colder than our comfortable temperature. When I used to work at the office, I snuck in a small inconspicuous heater for my legs under my desk.
http://www.independent.co.uk/news/uk/home-news/women-frozen-out-by-office-aircon-systems-designed-for-male-comfort-scientists-find-10436035.html
If the average corporate man would get rid of those ridiculous suit & tie costumes and the average corporate woman would get rid of the silly thin dress & blouse uniforms, we could normalize the temps in workplace and everyone would be happy.
I wear a clean t-shirt & jeans to work year round. In the winter (or what
passes for that in the desert) I put on an extra shirt on top. If corporate America simply stopped dressing up like it’s an episode of Mad Men when it’s 100 degrees outside, we’d have a much better off and actually use far less energy as a result.
I’m a firm believer in Formal Friday. Monday through Thursday should be casual.
Regrettably some jobs like banking or law (and others) will never switch to that. We still very much live in a time where what you wear is important to how others perceive you.
Well, we eventually got over powdered wigs, snuff boxes and corsets. Time now, finally, to abandon the wool suit jacket (except for cooler months) and so-called female business attire that purposely uncomfortable.
My opinion of bankers and lawyers is generally fairly low
(except the ones who go out of their way to help the poor
. . . and I know of some who actually do,) but I’m not all that surprised that most of them will persist in their year round Halloween celebration.
In high-tech, virtually no one (save the occasional salesman) wears the clown suit you describe. People come to my company in shorts. At a small company I worked for (75 people) the CEO wore sweatpants and an undershirt.
I have friends who work behind-the-scenes in banking and investment, and while they’re required to wear a collared shirt and dress slacks, none of them wear a suit and tie.
Excellent post, Marion. AC in office buildings is generally designed and air temperatures set so the Management staff can be comfortable sitting in their suits and sport coats. Idiotic dress conventions are part of the problem.
The other half is due to penny pinching HVAC installations which distribute the conditioned air to all the wrong locations in the buildings so some employees need thermal underwear while others sweat
“It’s not the heat, it’s the humidity” is really true. The Wash. DC area is basically a filled in swamp. When I lived and worked there I kept the temperature low because I was dripping sweat even in what I now (living in CA) consider comfortably mild temperatures. A dehumidifier would help a lot in keeping the AC from being set too low.
That’s what I think. Perhaps Wash is the proper description! Quite a few people seem reluctant to use AC as it doesn’t feel entirely natural. Could it be the humidity? I’m puzzled because I thought the systems reduced it; maybe not by enough.
An AC will dehumidify air saturated with water vapor somewhat, since cooler air can hold less water than warm air (this water is left in the condensor of the AC unit).
The problem is that while absolute humidity falls (fewer kilos of water per kilo of air), the relative humidity stays the same – near saturation. Unfortunately, animals are sensitive to relative humidity rather than absolute humidity.
To solve that, you need an AC controlled not just by a thermostat, but also by a humidistat. Those combined units are terribly inefficient though: they work by cooling the air further than required and then letting it warm up back to the desired temperature.
If you want to see graphically why this works, look at a Mollier diagram: http://docs.engineeringtoolbox.com/documents/27/AirPsychrometricChart.gif
A much more efficient but more complicated alternative is dessicant dehumidification, which is widely used in industry. The idea is to put a unit filled with hygroscopic material (a powder that sucks moisture out of the surrounding air) in the room and then to ferry the saturated powder into a second outside unit where the powder is heated until it releases moisture back into the environment. Repeat.
Since heating is much more efficient than cooling, such units are great for the environment. I haven’t seen a compact design though.
That I would question.. I see it all the time in Cairns, A/C full bore to get the humidity out of the air – but creating so cold rooms that the windows condense from the outside.
Also, those combination units just use a part of the cycle heat that would be released to the outdoors via the outdoor units heat exchanger by having some of that heat put into the indoors unit.. it’s just another valve in the indoor unit to be frank.
So the cycle gas isn’t all relieved in the outdoor unit but also in the indoor unit thereby releasing some process heat to the indoor air to get it back up in temperature and by that reducing relative humidity.
It’s not more wasteful than the other units, just a bit smarter about what it does and needs some more valve/electronics – that’s why they are more expensive.
For A/C with dehumidification one needs to go for Daikin units.. all the other brands don’t seem to have it.
A/C in that sense is overloaded anyway as most airconditioners just chill or heat the air, but don’t condition it.
Marketing idiots.
The problem is that most dehumidifiers work by undercooling and then reheating air, which makes them less efficient than conventional AC units. Conditioned air feels better, but at a huge cost to the environment (see my above comment).
?!?
conventional A/C units work exactly the same if you want to reduce humidity – by under-cooling the air, condensing some of it on the indoor heat exchanger (a pipe goes to the outside or underground for drainage).
Problem then is (I know it from Cairns) that the shops/houses are cooled way to far to get the humidity out and the air is too cold..
I got some small extra mobile dehumidifier units here that just run the cooled dehumidified air by the waste-heat exchanger, so net they heat up air, but they also catch ~6L of water for 4 persons in a small bathroom (towels and shower drying).
Uses about 200W electric energy. And isusually switched off over night (noise), but runs for the remainder of the day (~16 hours maybe ?).
Totally forgot.. healthy for indoors is about 60-70% RH.. above those levels fungi, mould and mildew grows.
Especially 0-energy houses with central HVAC for erngy recuperation need extra humidification/dehumidification, as other wise you risk health issues. Back in the old days the doors, windows and chimneys left air through so one had always a more or less healthy indoor climate & fresh air, but with all the energy saving one needs to do a lot more these days to create a healthy indoors atmosphere.
We get our “dry heat” in Arizona in late May and June: 100 degree F daytime high temps and bone dry, with humidly levels in the single digits. At night, with such low humidity, the temperatures cool off quite fast. It’s in the mid 70s by early evening and down to the mid 60s by late night. All in all, not bad.
But the monsoon season starts by early July and humidity levels rise to 50%.
100 degrees feels VERY different then. We also don’t get the early evening cool off with that humidity. It’s not uncommon by late summer to witness 85 degrees at 10PM and nighttime lows in the upper 70s. And, yeah, sticky. This sort of weather
can last into late September or early October.
Air conditioning? Bring it on! Especially in the late humid summer. If we finally legislate that all new construction has to obtain proper passive heating/cooling performance, we wouldn’t need as much of it. But that’s going to take
generations to properly address.
What I don’t get is the opposite reaction we get down here in the desert during the winter months, when it’s an absolutely beautiful 70 degrees outside and you walk into a store or public building with the heat cranked up to 80.
Well any building anyplace should have to be build to take the local climate into account, anything else to me is ineffective or maybe even stupid (in my opinion).
Yes, you would think. But much building in the post-WWII years was done in a brain dead fashion. During the second World War, when
fuel rationing in the US was very real, there was a modern architectural movement afoot that emphasized passive solar heating/cooling. This all disappeared in the brainless 1950’s, when
“too cheap to meter” nuclear energy trumped all that. For the most part, this sort of thing continued unabated through the rest of the century.
It’s only recently that we have seen net zero building coming online. The problem is that it’s not very practical to wipe out half a century of inefficient building to save energy. We can put bandaids (insulation, etc.) on the better ones, but we have to wait generations befor old buildings wear out and newer, more energy efficient ones, can come online.
Not so fast about bandaids.
San Francisco City Hall ( a gorgeously overdone Belles Arts style building ) just turned 100 years old and was awarded LEED Platinum.
Our house was built in the early 1960’s (equally brain dead period) and was an oven during the Summer and an Icebox in the Winter. We put in some insulation, double-paned windows, and shade trees and we never, ever use the big air conditioner on wheels I bought way back. We hardly ever turn on the heat in the Winter – big windows let in the sun during the day and heat-retaining tile-over-cement floors retain it at night.
I see lots of people around here doing the same. A few simple fixes can do wonders.
Apart from what Michael so rightly pointed out, it’s also a bad idea to let buildings get worn out and replace them. The embodied energy of a building is massive; simply upgrading an existing one is more environmentally benign than a new build even if that new build is quite a bit more efficient.
Architect Lloyd Alter over at TreeHugger does some good reporting on this too often ignored fact. See http://www.treehugger.com/green-architecture/proof-greenest-building-one-already-standing-released-new-report-preservation-green-lab.html or http://www.treehugger.com/sustainable-product-design/the-carbon-footprint-of-a-renovation-vs-new-construction.html
I’m currently going through my second AZ summer. It doesn’t feel as bad as the 1st one. Now when I walk outside and its only 100° I think it feels okay. Its funny though, people in the winter had the heater to 80°. I thought they were insane but I guess if you live there your whole life anything under 80 is too cold. Haha.
Welcome. It gets easier as the years go by. But the combination of global climate change and expanded urban heat island effect in the cities has meant generally hotter Arizona summers in recent decades
(I’m on my 32nd summer here.) More bicycles and electric cars help. So does smart landscaping with indigenous plants that use less water and less cement/blacktop on properties overall. Harvest your rainwater, since we’re going to run out of that before anything else. Solar on the roof is also a no brainer, if you can convince the utilities that this actually makes sense and for them to not continue burning coal or building new gas powerplants.
This really highlights why energy storage at a utility-scale is so desirable. Having Megawatts of battery capacity to buffer the peaks will allow utilities to turn down the output. Tesla Energy should really in a good position to capture this market starting next year.
Battery storage does not adress the huge seasonal variation in power demand – they are meant for intraday storage, not for seasonal storage (that would imply (a) building gigawatt-scale storage and (b) using it only sparingly).
Batteries might help deal with the high demand during the early evening by storing some excess solar from noon, but that’s about it. And given that quite a few AC-heavy areas have strong winds during the evening (but not during daytime), one wonders if simply building a bit more wind power does not work out cheaper than storage. Add biogas for extra flexibility.
And small nitpick: Tesla neither manufactures nor designs batteries, it simply rebadges Panasonic cells.
> And small nitpick: Tesla neither manufactures nor designs batteries, it simply rebadges Panasonic cells.
I mentioned “next year” for a reason. 🙂
Even then, it will still use Panasonic technology to produce Panasonic cells – just in their own building this time.
Yeah, that’s one of my workplaces. Long periods of low physical activity are enforced by the job demands, and combined with over-cooled temps, it gets pretty tough. Many of us working in that space make sure we have 3 layers to wear. In winter it sometimes gets too hot when the building switches into ‘heating mode.’
While I certainly respect a lot of the work RMI does, they don’t always take into consideration all alternatives. For example, I live in Arizona were 110 F summer temperatures are quite common. I can assure you that given 100% implementation of everything RMI recommends or could engineer is NOT going to eliminate the need for AC.
It is also probably true that I use about the same amount of electricity in my high efficiency heat pump to cool my home as someone living in Minnesota uses in oil or electricity to stay warm in the winter. The moral of the story is – it all depends on where you live doesn’t it.
But I have to put some of the blame squarely on the shoulders of our outdated AC or heat pump architectural standards we have in America. For example we are still building homes in America with heating and cooling ducts running through either hot or cold attics depending on where you live. RMI will tell you that about 15-25% of all your heating or cooling is lost in those ducts. All heating and cooling ducts should be within the insulated building envelope.
And this practice of placing packaged AC/heat pump units on roofs which we do in many parts of the U.S. borders on insanity if you ask me. Did you know it can be 20-40 F hotter on a roof than on the shaded side of a home, business or apartment building. And with the ratings of AC and heat pumps units measured at a steady state temperature of 85 F; installing a unit on a roof where it is 130 F makes no sense at all.
And did you know that almost every AC/heat pump unit cycles off and on several times every hours. Please realize that these are anywhere from 2 hp to 4 hp electric motors starting and stopping. All of these starting and stopping electric motors lead to a lot of peaks and valleys in the grid. And just for a minute lets talk about SEER or SER. This rating system is about as useful as trying to use a hair dryer to heat a house when its -20 F outside. Just ask your neighbor what SEER or SER means and wait for the blank stare. We need a AC/heat pump rating system “we the people” can understand. Oh sure its just fine for industry and government regulatory agencies to use these standards but we need something homeowners can understand.
And AC/heat pump efficiency. Do you know that most homeowners STILL TO THIS DAY buy a new AC/heat pump unit based on the cheapest contractors bid and have no idea how much it is going to cost them to operate the unit. In Europe and Asia almost all of their AC/heat pump units are inverter units with SEER ratings of about 20 or more. Here in the U.S. we are still giving the American people 14 SEER junk. For each one [1] SEER difference in efficiency about 6% less electricity is used. So that jump from 14 SEER to 20 SEER can save you about 36% on your electricity bill. And not only that; inverter units match the needed heating or cooling capacity by varying the speed of the unit or how hard it works. That means fewer starts and stops which results in less stress on the equipment, less grid instability and more comfort since there is less temperature variations for the business or homeowner.
I could go on for hours but there is so much low hanging fruit to be picked when it comes to energy conservation it isn’t even funny. As a country we should just outlaw the use of old start stop AC/heat pump technology. While it may cost a few bucks more in the beginning for a different compress and power supply board, when mass production is implemented the units will most likely be no more expensive than the old junk we are now selling.
And my dear friends, PLEASE DON’T ever buy a roll around AC unit with only one hose that goes out the window. That one hose is sucking the cool air out of the room the unit is in that you just paid the electric company to cool. Single hose roll around units use the cool air in the room to cool the operating unit. Most wasteful engineering design I have ever seen. If you must buy a roll around unit make sure it has two [2] hoses. One to bring in the outside air to cool the unit and one to discharge the hot air outside.
Have a great day everyone.
While I agree with almost everything you say, the comment about start-stop operation is odd. The compressors used (often scroll compressors) are perfectly well suited to such operation, and it saves huge amounts of power. Frequency regulated compressors offer an alternative, but at considerable cost.
As for grid stress: that only holds true if you assume all AC units cycle synchronously. They don’t, for the simple reason that no two buildings and no two AC units are identical. Over a wide geographical area, start-stop operation can still produce a smooth demand curve.
Other than that, excellent post.
Thank you for the kudos on the posting and yes you are correct. In almost every cases the spikes and surges are currently of little importance when you think about a few 3 hp, 240 Volt electric motor connected to a 1 MW 6.9 kV grid segment. This will only becomes a consideration as we install more and more solar in the desert Southwest where local distributed generation systems are beginning to occur. The in-rush surge current can be significant on smaller distributed grid segments. Also as the grid becomes electronically smarter, line noise will become more important.
So, worst case, we’ll need to site some of our storage close to the solar farms in order to smooth out the feed.
I really doubt that solar really slams on and off as the Sun rises and sets or patchy clouds drift over.
Nothing like a large thermal plant shutting down unexpectedly.
I agree.
We lucked out with our 1982 home, as far as energy efficiency goes. It’s a split level, well technically a bi-level, and so it has a fully finished lower level (8′ ceilings) 50% below grade and duct work between the two floors. It’s very energy efficient by design, but we bought it because of location, ample living space, and great upkeep. Having a liveable basement is also nice when tornado warnings are issued, but it does require dehumidification in the summer here in the mid-west. The heat pump with humidistat takes care of this and keeps it around 50% RH with inside temps 78F upstairs during the day and 70F downstairs due to cool air settling into the lower level between AC cycles (single speed unit). The winter is better because we can run the low speed air handler fan all the time (30 watts) because there is no water on the indoor evaporator coil. I think this is a major HVAC design limitation of combining AC and air handling together in two story dwellings in humid locations. To solve this dilemma, we may go with one or two separate mini-split units and keep the existing air handler for low speed distribution. The current central split heat pumps on the market are really all too large (>= 2 ton). The USA HVAC industry is still living in the past.
Excellent posting. It sounds like you are fully aware of just how wonderful that free stored “cool” in the earth/soil can be.
Now if there was just some way to reduce the cost of digging trenches or wells for ground source heat pumps what a wonderful world it would be.
For new construction, either ground source heat pumps and/or a well designed passive construction is the way to go. Due to yard space constraints and cost, we are stuck with air source as a solution. Moving the lower level or “basement” air upstairs is our form of ground source temp. moderation. I just need to make it work during the summer without raising the humidity in our home.
Some systems are put in in with ‘no disturb trenching’. Basically a narrow trench is dug at each end of the runs and a horizontal line is ‘bored’ in between the two trenches.
This is commonly done with sewer line replacement. Many plumbing companies already have the equipment.
Air source heat pumps in heating dominant locations (mid-west, NE) are still a mystery to homeowners and HVAC companies alike. In such locations, homeowners generally don’t know how to run them efficiently and HVAC companies sell them based on SEER, even though heating uses 2x+ the amount of energy. HSPF is the most important criteria for heating dominant locations.
My neighbor thought he was getting the most efficient new heat pump on the market because it’s 21.5 SEER, variable speed, etc. I didn’t spoil his enthusiasm by telling him that the HSPF rating is only 10 and not the industry leading 13 for split systems. I did tell him that 3 tons (36K btus/hr) capacity is likely way too large for his home (identical to mine). He bought their sales pitch, but at least it’s substantially better than the resistance electric furnace and AC combo he used to have. So even though his new unit has a variable speed compressor, it still cycles on and off a lot because the capacity is too big to begin with. I did help him by turning off resistance heating during defrost cycles and also turned off resistance backup heating above 5F. He is frugal like me and was NOT instructed by the HVAC company on how to set the unit for maximum efficiency. Sometimes I think the HVAC industry in the USA gets kickbacks from the electric utility industry for maximizing consumption!
I couldn’t agree more with your posting and more neighbors like yourself would be a good thing 🙂
I certainly understand the desire of some contractors to UP-SELL to a bigger unit or in some cases to just “make sure” the unit is big enough; but after the fact, there isn’t a whole lot more that can be done. The unit is probably just be too big.
The industry standards used to calculate heat load to me seem to be very conservative on the PLUS side. For example, according to calculations, my home should have a 3.5 ton [42,000 BTU] heat pump. However in practice, my duty cycle even on the hottest day has never exceeded 60% [run time] according to my digital thermostat. Even my local utility has seen the weakness in the methods currently used to calculate heat load and now offer a $250.00 rebate to homeowners to downsize units 1/2 ton or 6000 BTU’s. It seems they also realize that too many people are installing units too large for their homes.
We’re using a 2.5 ton unit with HSPF 8.5, 13 SEER from 2001. It actually has enough heating capacity for 99% of our heating needs without any backup electric strip heat. I estimate our balance point between 0F and -5F. So from a heating standpoint, it was sized correctly back in ’01 when I bought it and knew little about heat pumps. I estimate that our greatest heating demand was only 9-10K btus/hr., averaged over a 24 hour period, this past winter. I’m really in the market for a 1-1.5 ton variable speed split unit that cycles down to 20% of capacity, but they don’t make such a product right now.
Our unit is definitely cooling oversized as it cycles on and off all the time. I need to install a run time guage to get a more exact reading of compressor use during the AC season.
My neighbor was sold a 3 ton unit, which is sized for heating purposes, even though its 15% more efficient than our unit. As you may guess, it cycles a lot during the less demanding summer season.
Neither this story nor RMI has claimed that all AC should be removed. But dressing more in line with the weather, and not over AC’ing a building is common sense.
Yup makes sense to me Matt. I heat my home to about 65 F in the winter and cool it to 78 F in the summer. Very comfortable at those temps.
This looks like a wonderful new low energy building. I like the personal DC fans and seat heating for chairs, it reminds me of seat heating in our Nissan Leaf.
Passive design is so useful to minimize HVAC and lighting needs, but I never see it in practice around here. There is so much missed opportunity in the new homes and offices still being built.
I’m optimistic about retrofitting for energy efficiency. From smaller more efficient HVAC (mini-splits), to low voltage solar fed DC branch circuits (backed up by AC), to micro compressors useful for all kinds of localized needs. Add in better doors, windows, and insulation, and you have a low energy economy perfect for renewable energy.
We’ve reduced our electricity consumption 30% since 2001, and this puts us in the top 5% for low energy use among 100 comparable all electric homes. I’m looking to reduce it another 50% in the coming years and powering it from (mostly) the sun.
These are great ideas, but there aren’t many places in the USA that can contemplate total omission of cooling, and why should they when reversible heat pumps should be the baseline? It’s also disappointing not to see the words geothermal or ground source here. And there needs to be more emphasis placed on smart controls, because not many buildings have competent controls and so they are out of control. Just running the cooling full bore accounts for most cases of excessive cooling, IMO.