The Math of Lower Thermostats

Partial Sun no Problem for Solar Panels

I happened to be cleaning a boiler this morning at the home of one of my solar clients, and i checked the system over.  50 degrees out, cloudy enough so that I couldn’t tellwhere the sun was in the sky. The two Heliodyne panels were reading 95 degrees, the pump was cranking away, and the two 60 gallon storage tanks were being warmed. All in weather not normally seen as optimal for solar hot water systems. The oil fired boiler in this system only has to raise the water temperature to 130 degrees to serve the dishwasher, laundry and showers. Lots of energy was being saved by the solar equipment in that house.

I didn’t build the panels, or the heat exchanger, but I did design and install the system. It performs beyond expectations. The new optically selective coatings being used on flat plate panels will collect photons and transform them into heat much more efficiently than flat black paint or a bare surface.

This is a short post, an update on some things we’ve discussed lately. Don’t believe the dismissive comments about solar hot water being a three or four month blessing. Solar hot water, thoughtfully installed, will perform for you on sunny days twelve months a year in New England. Connected as a pre-heating treatment with an energy source configured to finish the water off to usable temperatures, solar panels can be working for you all winter long, even on cloudy days.

Phil’s 113th Energy Dream

The diagram at left teaches you more than most folks want to know about boiler internals, specifically horizontal three-pass cast iron. There are many clever variations on the theme of torturing hot fumes before releasing them to the chimney and the heavens, and this one has been used for two generations in big commercial boilers powering factories and hospitals. Only lately do we rise above the heavy, hollow cast units many of you still have in the basement.

Don’t think me smug, I service boilers performing at 75% efficiency all over the county, and the Biasi in my attic gets around 87%. There’s not a huge harvest of energy to be reaped yet from changing boiler designs until we find a way to deal with the acids and sludge condensed in boilers at lower temperatures. In Europe they’ve refined the sulfur almost entirely out of their fuel, yielding something almost as clear as kerosene. The link is to a British site listing oil boilers boasting 97& efficiency. Shame on us Yanks. I won’t delve into the technology of boilers with condensing exhaust, but just imagine something vented through a light metal tube at less than 200 degrees, with sulfuric acid and dissolved ash dripping from a draincock on the flue.

   My Biasi is among the high society of  boilers sold in the US,  but it hails from Italy. Its nearest competitors are made in Germany, Germany and Italy, respectively. There are American multipass designs being sold, but they lag behind in the critical qualities of low mass, low volume and low stack temperatures. Makes you think, don’t it? At app. 2.10 US dollars per gallon on Labor Day weekend, heating oil is as cheap as it’s been in years, and we Americans see no reason to respond, apparently, to anything but brute market forces. Price, in other words.

 The little B4 model weighs in at 300 lb. dry weight. We hauled it up through the scuttle hatch with a light comealong rigged to a single unbraced rafter. Piece of cake. Why am I in such a lather to get it up there? It doesn’t require a conventional chimney (my house doesn’t have a conventional chimney), and the vent is through a single length of capped stainless steel chimney pipe extending through the roof on the leeward side of the house. It’s also within 6 feet of the blower unit that heats my house. The water heated by the boiler travels no distance at all, losing almost no heat to the surrounding air. It sits in a metal pan piped to a nearby sewer vent pipe.

  For domestic hot water, imagine a stainless steel block heat exchanger the size of a shoebox hanging off the back of the boiler. When someone hits a switch either in the kitchen or bath, the control starts the boiler water circulating through the exchanger, heating domestic water in one pass hot enough to do dishes, shower or operate the laundry. But you have to hit the switch, otherwise the little Biasi sits there cold. Time to hot water, from a standing start? Three minutes by the stopwatch. I know, America can’t wait for its hot water, and can’t be bothered to hit a switch. But this is how it goes at my house. You get up to an hour of glorious hot water from a twist of the timer. Otherwise you wash your hands in cool or tepid water warmed a little by its passage through the house pipes.

Antifreeze protects the boiler, blower coil and heat exchanger from freeze damage, and the attic is insulated against bitter outdoor temperatures. I have to use a little pump, fashioned from an old oil burner, to lift fuel to the attic for the boiler. That adapted unit sits in the basement next to the oil tanks, pushing a dribble of oil up to a heavy steel reservoir which feeds the burner by gravity. My house, insulated through various remodeling projects over thirty years to respectable R values and tightness, will be comfortable this winter without any renewable energy resources other than some carefully planned passive solar (click to see an older post on our sunroom).

Will I put a system like this one in your house? Not until we talk. Talk a lot. Show me your old copies of the Whole Earth Catalog, or the original pulp-format Mother Earth News. Tell me you were at Woodstock, and why I didn’t see you there (I missed Woodstock, that’s why). Show me your green-friendly stock portfolio, your Energy Star appliances, your first pair of Birkenstocks. And assure me you’re willing to wait three minutes for hot water at any tap in the house, think before you hit the switch whether you really want to spend that energy, and let Dirty Phil into your house at least once a year for a boiler cleaning and efficiency check. And then, maybe. How can I be sure you’re ready to take this step? Soon I’ll be blogging about the solar hot water system that will be incorporated into my attic this fall. Stay tuned.

More Hot Water Options, and My Favorite

The photo is borrowed from a charming blog post dealing with gender differences in showering styles. But we’re here to wrap up, for now, the subject of domestic hot water options for energy conscious homeowners.

We’ve talked about tankless water heaters, solar water heaters, electric tanks and furnace coils. Here are a few more to round out the picture for you.

If you have a coil in your oil or gas fired  boiler, you might consider upgrading to an indirect hot water tank. There are two styles, one in which boiler water fills the tank, and one in which boiler water fills only a coil in the tank. My favorite is the former, for efficiency. This link is for an excellent design by Dunkirk. The boiler is relieved of its duty to stay hot as heck all the time, running only when a tank thermostat calls for it to warm up the tank, or when hot water is being used. You save considerable on “standby losses” and seldom experience a delay of hot water due to the tank’s capacity. The insulation of the tank makes it a better reservoir for heat, and you can over-wrap it yourself and do even better.

There is also the option of putting the oil burner right under the tank and heating it up directly. A “direct fired hot water heater” is a tank sitting over a firebox with a burner and a flue. Standby losses are a bit greater with the direct design, but the recovery rate of the tank temperature is amazing, and it’s hard to run out of hot water even with teenagers in the house.

I recommend you use the link and look at what Energy Kinetics has done with the concept of hot water production and standby losses. Their systems are pricey and require considerable expertise to install correctly, but the savings give you an accelerated payback over the classic cast iron boiler with internal hot water coil. A smart controller starts the low mass (low mass, low volume, quick heatup, small amount of energy trapped in boiler upon shutdown) stainless boiler up cold, turns on a circulator to respond to heating needs, and circulates boiler water through a flat plate heat exchanger piped outside of the boiler. domestic hot water is heated in one pass, or a separate circulator warms a well insulated storage tank to provide water that doesn’t fluctuate much in temperature (this temperature fluctuation is the most common complaint from boiler coil people, other than high energy costs). At the end of a heating/hot water cycle, the boiler circulator stays on until the heat has been “dumped” into a waiting zone or the hot water tank. Not much gets wasted. I seldom directly plug a company in this blog, but no one else is doing exactly what Energy Kinetics is doing, and I think they’re ahead of their time in a notoriously sluggish industry in a notoriously energy-spoiled culture. Good for them.

Next post I’ll talk about the system I just installed in my own house, a real pound puppy of assembled energy efficient components crafted to my own design. Stay with us……  meanwhile, if you’d like to discuss your own options for upgrading your hot water system, hit the contact link and i’ll be happy to respond.

One More Reason to Hate Skinny People- They Stay Cooler

There are no Models any more; only “supermodels” and “weight loss contestants.” The woman in the silhouette photo at left may be an expensive sweetheart in many ways, but the physics says she’s at least easier to keep cool.

It’s almost a “duh” moment to reveal that skinny people stay cool at higher temperatures, I suppose. But since I stopped being skinny, I’ve been indulging in denial about my need for greater cooling comfort. At two hundred pounds of aging manhood, I suffer a bit more in the heat and humidity than I did a few years ago. And you?

A Hawaiian blogger from Hilo cites a study exploring the relationship between body mass and the need for more cooling. Apparently larger, heavier people expend fewer calories through normal indoor activity, but they require lower AC temps even so. Ok, I get that. And there’s a twist. The study poses the question whether the popularity of largeness has itself causes our increasing dependence upon mechanical cooling, or whether THE AIR CONDITIONING ITSELF HAS CAUSED US TO GET FATTER!

As Dave Barry often says, I am sooooooo not making this up. If reducing our heat stress in summer causes us to eat more, ok, maybe. If reducing our heat stress simply permits larger people to survive summer, ok, maybe. Or if heat stress is a weight loss technique we should all be considering, well, I don’t like it, but maybe.

In the case of my embarrassing spread, I don’t think my air conditioner is the real perp. I think I did it to myself. But a guilty air conditioner may cost less to run. I can be stingier with the thermostat. I can do yoga in front of the TV. I can eat salad with almost no dresssing while i do yoga in front of the TV, occasionally glaring at the thermostat. I can work in the heat all day and come home to a cool house, drink ice water and bask in the relief from heat stress. I don’t think I should swelter until I reach my ideal weight. I think I may live longer if I don’t have to court heat exhaustion, dehydration, depression, grouchiness, malaise and unpleasant body odors when it gets hot outside.

I want my AC. Forget the study linking obesity with air conditioning. I can adjust. I’ll drink so much water I won’t even be hungry. And if the supermodel gets chilly, she can go outside and pose……..

Smell That Fresh Air! Where Do YOU Live?

I put good filters into the HVAC equipment I install. Sometimes, on request, I install special electronic or ultraviolet purifiers that remove living thingies from the air inside your house. But that’s only inside. We can battle the pet dander, dust mites, pollen and even germs floating in your indoor air. But we can’t fight what ’s going on outside.

The air quality where you live depends upon many things: surrounding plant life, animals living nearby, cities and manufacturing plants upwind of you, and nuclear testing in China, believe it or not. If you live just outside, say, Gary, Indiana, or on the east side of the Bronx, or in LA during smog season, you have to live with what man does to the environment in the course of American living: automobile exhaust, industrial emissions and the smoke from too many chimneys affect us when we breathe.

But I live in the country! Miles and miles of luxurious forest, hayfields, amber waves of grain, native casinos (non-emitters, they swear, very harmonious wit’ nature), placid cattle grazing in fields fenced by rubble-stone walls. I love New England. But the air quality where I live is not free of challenge. Ragweed, milkweed, conifer pollen, asters, wild grasses, oak and the cows’  behinds all emit stuff that I’m allergic to. On sultry August days I have to come inside sometimes to catch a breath of clean air. My house is not a clean-room, but it has a filtered air conditioning system that stands between me and the bad stuff outdoors sometimes when things build up and the Air Quality Index shows a high level of pollutants in the air.

If you’re not susceptible to these changes in air quality, good for you. But most people are, to varying degrees. Even stalwart smokers notice when the air gets heavy with dust, pollen and smoke particles, and breathing can be actually risky for more sensitive types like asthma sufferers.

What to do?  I’m afraid the solution, like so much of life, involves work. To start with, clean your house. Really clean. Use a good vacuum, preferably a hypo-allergenic model, or even a HEPA quality vac, move the piles in the corners, move the couch, move the dog, and vacuum everywhere. Do the walls, too. I’ll wait while you finish.

And vacuum your bare mattress to reduce the number of dust mites living there. What are they living on, you ask? Read the Wiki thing in the link. Or don’t.  Dust mites are icky. Just vacuum your mattress, under your bed, run your bedding through the dryer at high temp once in a while, or, better yet, hang it out on a hot sunny day. Dust mites are like vampires. Sort of.

And once y0ur house is clean, keep it clean. Fry your favorite greasy foods out on the grille rather than indoors. Use a non-ozone air purifier to filter one safe space in your house for you to lurk in on bad air days. Watch the weather thingie for air reports; they’re there, but barely. Don’t look for them in the shots of the weather lady’s legs.

And consider, charming as they may be, that your pets may be part of the problem. Especially if they share your furniture or your beds when you’re not looking. And they do, don’t they? Don’t lie. Of course you love your pets; but they might be as big a factor in your allergies as the ragweed pollen that’s out and bothering everyone now.

Respiratory health is not something you can take in pill form. What goes into your lungs can cause you trouble. Sometimes it comes from upwind, from the factory or the city. Sometimes it comes from the scenic fields and woods around your house. Sometimes it comes from the mattress under your sheets. Or from your dog. And if it’s coming from inside your house, there’s something you can do about it. Those fields may be best viewed through your windows until pollen season is over. Health is an energy issue, as we will see in future posts.

Ductless Split Air Conditioners – Practically Perfect

If your home has a large open space built around, perhaps, the kitchen, dining room and den, or the newfangled Great Room concept, you can render that space comfortable without sacrificing your windows or paying big sums for some guy like me to install a full duct network for a central system. You can have a “ductless split” system installed, operate it from a handy remote, and cool the large living area of your house in respectable silence.

Window units are noisy and take up window openings. Central systems are the best, but can you afford one right now? Like the incumbent Democratic administration, I favor a considered compromise when all factors can be weighed.  I don’t favor any single brand, but i do insist that you shop for these essentals:  high efficiency, ample capacity, multiple fan speeds, and a good warrantee. Here are some links, offered without partiality for your consideration. Here’s a multi-brand site, another one, and a brand or two of the better ones. 

To find an installer, you may have to call around, use the Yellow Pages, and ask at the wholesaler’s, because not all techs are familiar with the subtle ways of the ductless split. Expect the job to take less than a day, and expect to be cool by dinnertime. The hardest part is tying the electric power into your panel, a process that may require a licensed electrician. Be sure to ask if your installer does the wiring himself.

The thermostat’s in the remote, the filter is the washable kind, and the condenser is as energy-efficient as the outdoor unit of a central system, and a bit more efficient than any window unit you can buy. Ductless split is less noisy than window units, slightly more noisy than central, typically.

Here in New England, we have the possible need for home air conditioning, I tell my clients, of about 100 days per year. Most folks use their air conditioning between 40 and 60 days, unless a bust of ralph nader adorns your mantel and you’re reading this while completely naked. How much will it cost to get you through the summer? Can you hide in your bedroom next to the window unit? Do you need the whole house cooled and dried to accommodate your teenagers and your expansive tush sticking to your naugahyde recliner? Or somewhere in between? If you’d like to get comfortable in the dining room and huddle around the table like millennial Waltons being cool, and if you’re tempted to break out the sleeping bags and have a camping adventure on the family room carpet, you could be enjoying your ductless split system by, say, tomorrow night.

Air Conditioning– It’s All About Water

      In summer, no matter where you live, you sometimes wish for a cooler house. “Sultry” is the word they taught us in school for those days of heat and humidity that sap your energy and make you feel clammy and damp. The woman in the photo is using an ancient strategy, moving air across her skin to promote the evaporation of moisture, which removes heat from her body and dries her skin to a more comfortable level. Fans are always good.

But what happens on those days when fans don’t work? When the humidity is so near “dew point” that no evaporation is possible? When the air contains so much moisture at its current temperature that it can’t receive any more? You can drive to the beach or lake or pool and immerse yourself in water to cool down, or…..  

Enter air conditioning, a technology older than you might think, which cools the air in a space and, at its best, lowers the moisture content of the air so that evaporation can remove heat from people and animals therein. Simply blowing air across quantities of ice is an ancient application. Willis Carrier devised a refrigerating device that cooled air using ammonia as a compressible refrigerant in 1902. We now use non-toxic gases in home and auto air conditioners, but the environmental impact of those gases has us looking for the next generation of refrigerants that don’t pollute nearly as much. More on that another time.

Here, as I say often, is the secret: any air conditioner that can cool room air to a temperature below its dew point in one pass across its coils will eventually render a space comfortable for people and animals. Moisture drops out of the cooled air, drains off somewhere in a responsible way, and the air now feels more comfortable, breathable, drier, and the moisture evaporating from your skin is removing just over 1000 btu per pound of sweat. Don’t think too graphically about the idea of a pound of sweat, but athletes in extremis can shed ten pounds or more from perspiration and evaporation during a game or training session, and marathon runners dread humid days for races because they will sweat just as much but not be able to control their bodies’ temperature as well in those conditions. Just like you, in a milder way, on a hot day, entering a room full of cool, dry air. Wonderful. Or unable to find a cool space and wiping away pints (pounds) of perspiration and still feeling hot and miserable.

Today in my zip code it’s only 77 degrees Fahrenheit, but it’s 95% relative humidity. That means the air is burdened with 95% of the water it can contain at that temperature, and it’s unlikely to accept that last 5% without more wind than we have. It’s uncomfortable, sticky, still and not going to improve until thunderstorms come later in the day to reduce the humidity. Good day to use air conditioning to dry out the air inside, even though the temperature is not oppressive.

Even if you air condition only one special room in your house (bedroom, tv room, basement den) as a refuge on miserable days, you can give yourself a place to get comfy and avoid the toll of heat stress (the link is a bit lurid, beware). Or you can take a shower to cool down, hug the fan like the young woman in the photo, drink lots of iced stuff, and gripe about the weather to anyone who will listen. It seems to help, somehow.

The S.E.E.R. Predicts Your Energy Future

Do you mind the bad puns in the post titles? The label at left was attached to a new room air conditioner. SEER, or Seasonal Energy Effiiciency Rating, is an industry standard meant to help you compare appliances, specifically air conditioners, as to energy efficiency. A low number means lower efficiency, a higher number means greater efficiency and better performance for less energy.

   This Wiki link explains the higher math, but you can get it this way. SEER, in reference to AC units, is the raw number of btu you get from investing one watt for one hour. If you, like me, pay almost 20 cents per thousand (kilo-) watt hours, a SEER 0f 10.5 means you get back 10,500 btu for every kilowatt hour you invest in running the unit. That capacity matches a small room air conditioner, so you can figure you spend between 20 and 30 cents per hour to run your window air conditioner at that SEER. Run it day and night for a week, you’ve spent perhaps $40 US on average to air condition that room or space. Boring? Only until the power bill shows up.

   So the numbers matter as much as the price when you go to the big box store to shop for AC units. You might pay $50 less for a cheaper unit, but how long will that $50 last when a window unit of 9.8 (minimum) EER (category for room/window units) costs 30% more to run than a better one with an EER of 13?  The payback on the difference can be measured in weeks, or perhaps a New York minute.

If you install a central (ducted, noisy parts outside, air comes out of holes in floor or ceiling) system, the minimum SEER permitted in CT is 13. And you can spend some more money and get SEER ratings of up to 23. Yes. Almost twice as efficient. And almost twice as expensive. Equipment rated SEER 16 is more reasonable in price, and the energy savings will pay you back rather quickly for your initial investment in better equipment.

If you have large, open spaces in your house (no, I don’t mean missing walls and doors, silly), you might opt for a Ductless Split System, in which a single blower unit hangs on a wall and the noisy condenser sits outside. There is no hidden ductwork in the basement and you can control the unit with a handy remote. SEER can range from 13 to 16, and total system cost can be half the amount you pay for a central system. The ductwork I and my colleagues install is efficient and equity-enhancing, but expensive.

Numbers can be so boring unless dollar (or Euro) signs are attached. When you invest in air conditioners, don’t wait until it’s hot and you’re miserable and don’t have much money in your pocket. If you can help it. Get a grip, take along a calculator, crunch some simple numbers, tax the salesperson with hard questions about efficiency and capacity, and get more for your money—- not just today, but for as long as you own the equipment. We’ll talk more about the different systems in the next post.

It’s Not Rocket Science. Photovoltaic Cells Unmasked

      A faithful reader has commented on the DIY (do-it-yourself) potential of solar panel construction, and cited a source promising solar panel construction for extremely affordable sums. Here we are, not to debunk the claims of the “You Can Do It With My Special Video” entrepreneurs, but to give a framework of data to help you in your research.

A single solar cell consists of two wafers of highly engineered silicon, joined carefully by a conductive bond, fastened to a supporting backer, with electrical leads. That cell can typically generate .7 volts of direct current power. Connected in a cluster behind a clear glazing, the assembly, or “panel,” can be configured to deliver a maximum of 12, 24 or 48 volts direct current while sitting in the sun on your roof.

The catch, and there are a few, begins with efficiency. Silicon responds only to narrow frequencies of light, operates poorly at high temperatures, and seldom delivers, in many lower cost panels, more than 5% to 15% of the potential power of the sunlight falling on it.  Here’s a NASA link that explains some of the challenges and how they’re met. Optical reflectors, wafer stacking, and various cooling techniques can improve panel efficiency up to 20%. In my previous post, titled “3 kwh per square meter per day…” we did some math about the potential of any rooftop to deliver solar electricity, and this efficiency factor has to be part of that math. Even a well-constructed solar panel will only absorb and convert one watt in five in full sunlight.

Once the solar panel is on the roof and receiving sunlight, it needs to talk to a device that converts direct current to alternating current, which is the form of power distributed by utilities and used in your house. The Inverter, as it is called, massages that direct current of some lower voltage into alternating sine wave current at 120 or 240 volts for American homes to use. Voltage may vary by global region. The inverter operates at about 90% efficiency, depending upon a lot of factors, so use that in your calculations.

If your system will be tied to the grid, your panels and inverter will be specified and dictated by the utility. No home-brew systems that I’m aware of can be grid-tied with CL&P’s approval. The engineering of the specified inverters carefully matches grid voltage, among other things, and instantly shuts down the system if the grid loses power. This prevents the deaths of linepersons working during outages. It also prevents you from using your system, even if you manually disconnect it from the grid, during an outage.

As of this writing, photovoltaic panels can’t be bought at WalMart, except for specialty applications like charging lawnmower and car batteries, and powering tiny landscape lights. Solar panels are available through Home Depot in modest wattages, and they also subcontract installations in some regions. You cannot yet just fill up two shopping carts and be on the grid by sundown, at least not in Connecticut. In some ways the equipment is less complicated than the permits and inspections required by most utilities.

But we’re getting there. So, hats off to you DIY enthusiasts, I hope your time comes soon for affordability and regulatory friendliness. Meantime, you can do smaller projects at home, limited only by your purse and daring. Our time is coming, and your questions are always welcome.