Evaporative cooling: a low-budget yet energy-efficient way to improve thermal comfort in motor vehicles

The cost added by an air-conditioneer to an automobile goes beyond the retail price. During the vehicle's lifetime, the comfort charges its fare. Apart from the usual increasement on the fuel consumption, since usually the compressor is driven by the vehicle's own engine, also sacrificing the performance in certain occasions (most notably in vehicles with smaller engines, of course), a regular air-conditionner for automotive applications also implies a few more procedures to the maintenance routine, due to items such as belts and pulleys required to drive the compressor, and eventually some recharges of the refrigeration gas. A few decades ago, the most usual refrigeration gas was the CFC (Chlorine - Fluor - Carbide), also known as Freon, which is regarded as an environmentally-harmful compound due to its effect to the ozone layer, and there are still some older vehicles operating with this gas instead of the HFC-134a currently prevalent.

Brazilian Volvo N10 with an evaporative cooler. The black box behind the side ladder is a water reservoir, while the roof-mounted white one is the evaporative unit.

Basically, there are very few options for those who don't consider getting rid of some sort of cooling device in their vehicles. An option which already went quite mainstream is evaporative cooling, which got favored by many truck drivers in South America (most notably Brazil, Argentina and Uruguay) due to the ability to remain operating after the engine shutdown, since it doesn't rely on an engine-driven compressor to perform its duty. Actually, has no compressor at all... Its operation is all-electric, but it doesn't put a significantly greater charge over the electric system than a simple forced-ventilation device would do...

Evaporative coolers are cheap and easy to retrofit even into older vehicles, such as this Mercedes-Benz L-1113

Considering some special applications such as hybrid-electric vehicles, like the Toyota Prius and the Chevrolet Volt, developed under a specific goal on energy-saving, the evaporative cooling is even more worthwhile. Due to the air-conditioneer of those models getting an electric-driven compressor, allowing it to remain operating when the internal-combustion engine is off, the loads at the electric system are significantly increased. An evaporative cooler has a lower energy expense, which seems to make more sense regarding a "clean" vehicle...

Another advantage is the purchase cost of an automotive evaporative cooler (often quoted in the United States and Canada as "swamp cooler"), which is on average more than 2 times cheaper than a regular air-conditioneer. Depending on the size of the vehicle's cab, the cost advantage can get even more favorable for evaporative cooling...

Brazilian Volkswagen Transporter (Kombi) fitted with 2 evaporative units: cheaper than an air-conditioneer and doesn't overload the underpowered 1.4L EA-111 flexfuel engine...

The operative principles are also different: an average air-conditioneer works thru the compression of a gas which circulates inside a set of metallic serpentines, leading to a partial condensation of the air humidity inside the refrigerated compartment, and subsequently the condensed water gets expelled to the outside. It's worth to note the dried air is often pointed as a source of respiratory nuisance. Meanwhile, an evaporative cooler has water directly sprayed into the air. The water ends up evaporating due to the heat absortion. A set of texturized filters avoid any ocurrence of dripping, in spite of the increasement on the air humidity.

This coach, fitted with air-conditioneer, has sealed windows, avoiding the passengers to keep them open.

It's also worth to remember that a regular air-conditioneer has its efficiency decreased when there is too much external air flow entering, while an evaporative cooler actually works more effectively when there is some external air flow. This ends up leading to some advantages for this setup, due to the health benefits of a higher ratio of air renovation inside the vehicle.

Brazilian metropolitan transit articulated bus, with a 210hp engine. Too underpowered for its size and weight, but even though a regular air-conditioneer wouldn't be the most suitable solution, it's not so hard to retrofit an evaporative cooling setup. The most usual evaporative units can easily bolt into the roof hatches...

In spite of the purchase and maintenance costs advantage, evaporative cooling has only two major disadvantages: its efficiency slightly decreased when the ambient relative air humidity is already high, and it can't provide heating autonomously. But after a detailed case study, pointing out the pros and cons of the operational scenarioes, evaporative cooling can be revealed as the best option for many customers.

Motorcycles: the most environmentally-suitable vehicles for Diesel-haters

Motorcycles are a kind of love-or-hate thing, usually bashed for the absence of comfort features or weather protection for the user, and lack of cargo space, making them unpractical to haul bigger objects. Their low fuel consumption can become appealing for people who hate Diesel-fueled cars, alongside the hybrids. But, considering the environmental aspect, the motorcycles make way more sense than a hybrid econobox, i.e. a Toyota Prius.

One of the main arguments towards hybrids, apart from the "motorcycle-like" lower fuel consumption comparing to an average non-hybrid econobox, was related to the permission to use it in HOV lanes even when the driver was forever alone. This benefit, which led to a massive amount of hybrids in places like Los Angeles, came to an end recently, since they don't qualify for alternative-fueled vehicle incentives anymore, altough it's still valid for motorcycles. Considering the lesser space taken at the road surface by a motorcycle proportionally to the passengers capacity, they also make more sense in matter of traffic jam reductions.

No matter if it's a tiny Lambretta or a big Harley-Davidson, the size-to-occupation density is higher, so less space is taken at the road surface for each person transported by them instead of a Prius.

Even an old-school motorcycle with a simple carburettor-fed engine can still get better mileage than a hybrid car, altough nowadays the electronic fuel injection becomes prevalent.

Another aspect to consider is the amount of raw materials involved in the manufacturing of the whole vehicle, replacement parts (i.e. tyres, lamps, spark plugs, coils and cables, shock absorbers, friction material for clutch and brakes, among others) and other products needed to keep the vehicle operating properly, such as lube oils and greases, no matter if the car is a subcompact such as the Chevrolet Spark or if the fuel consumption is not so much more advantageous for the motorcycle, it's still usually more efficient from the factory to the end-of-life disposal.

A specific application where motorcycles can show other advantages is recreational off-roading: dirt-bikes are usually even more compact and lighter than a road-legal one, which increases their maneuverability in tight spaces where a Jeep would be too big to pass safely.

The lower weight also copes to reducing the risk of getting stuck in a mud pit, and is also easier to recover if gets stuck. Environmentally-wise, apart from the lesser amount of fuel and lube oils, motorcycles generate a lower pressure over the soil, in spite of the smaller contact surface due to narrower tyres. Basically, assuming that the contact with the nature is an essential part of recreational off-roading, the only disadvantage of motorcycles in this application is the lesser capacity to carry passengers, tools and replacement parts (and also a grill, charcoal, some beef and beer for a tailgate party) comparing to a 4WD.

After all, motorcycles have been a good answer to the demand for fuel-efficiency and an overall low running cost.

Artesanal double-cabs: a former Brazilian trend, now nearly extinct

Starting in the 60's, going thru the 70's and 80's, artesanal double-cab conversions were a popular mod in Brazilian-made trucks, due to the unavailability of factory-equipped versions. If early ones were pretty simple, just a crew-cab work truck like that old blue Chevrolet C-10 fitted with a 250cu.in. Stovebolt Six and a collumn-shift 3-speed manual transmission, they started to become trendy after '76 due to automobile import restrictions, becoming an option to customers in the market for luxury cars, which then had a low availability. Larger rear cab extensions started to become prevalent, offering enought room for comfort features such as a sofa-bed and home appliances such as TV and fridge, to make longer trips more pleasurable.

Some models, such as the Chevrolet C-20 (which ethanol-powered versions were locally-named A-20 and Diesel ones D-20, and export ones B-10), started to have crew-cab versions in the 80's, but weren't so luxurious as the artesanal conversions. A curious feature to note is than most converted double-cab trucks had only 2 doors, once a trend in Brazilian market for budget reasons and concerns about child safety, while a crew-cab from the factory had 4 doors.

The 90's came with a market reopening, and Japanese crew-cab trucks started to hit the streets. With its smaller, more fuel-efficient engines, better maneuverability in tight spaces and improved driving comfort in opposition to full-size trucks which often still didn't even have power steering, started to take over the local truck market. The segment had nearly to reinvent it to survive. many conversion shops closed, others started to sell accessories to the Japanese newcomers, while a few still remain on this market.

Some models such as the Chevrolet S10, introduced to the Brazilian market only in '95 and since then the best-selling truck, had a potential market for crew-cab versions, which OEM extended-cab couldn't fully meet. Until '97, meanwhile a factory crew-cab wasn't available, the gap had to be filled by the aftermarket conversions. Even after that, some customers still enjoy the artesanal double-cabs since they provided more room to the back seat, making it more comfortable for family use and improving the comfort in longer trips.

The double-cab conversions market is still not extinct, in spite of the much lower volume. In addition to more traditional body-on-frame trucks such as the Ford F-250, it also started to draw more attention to unibody front-wheel drive coupé-utilities such as the Ford Courier which are very popular in Brazil in spite of the unavailability of a double-cab/crew-cab for most of those.

It may look dumb for some customers, but for many others it's important to have an open deck which makes easier to fit some larger bulks in a counterpoint to a regular sedan...

The only coupé-utility with an available double-cab is the Fiat Strada, in a response to few customers who were retrofitting rear bench seats into factory-offered extended-cab versions to carry 2 more passengers in spite of its tight space.

In spite of all the factors which led to its decline, the artesanal double-cab conversions are not fully extinct, mainly due to the ability to provide more personallized solutions than an OEM would, exactly due to its lower market volume...

Arguments against EPA witch-hunting regarding Diesels without mandatory emissions equipment

The EPA should reconsider the current strict mandate on Diesel road-legal emissions,regarding their particular operation in a counterpoint to a regular spark-ignited engine. Some devices such as the EGR and SCR actually just transfer the pollution from the truck's tailpipe to an industrial chimney.

The EGR (Exhaust Gas Recirculation) leads to an increasement in the Diesel fuel consumption, which can be easily diagnosed from the enhanced particulate matter emissions, altough the Diesel Particulate Filter (DPF) hides this problem. Due to its prejudicial interference in the combustion process, the EGR is not compatible with a more accurate tuning for fuel-savings, which could lead to imrpovements not just environmentally-wise but also regarding national security due to the lesser dependence on foreign oil from politically-unstable lands.

The DPF getting more demanded also leads to an increasement on the regeneration cycles required to keep its operational conditions, also enhancing the Diesel fuel consumption. We all know the oil drilling, refining and logistics involved in the final destination of its derived products (gasoline, Diesel fuel, kerosene, among others) have its own environmental impact and a high energy expense, enhanced due to the misguided EPA standards which are actually not so effective concerning to environment protection.

Another currently-mandatory device, the SCR (Selective Catalyst Reduction) is also not so “clean”, since it increases the logistics complexity involved in Diesel vehicles' operation and leads to a high consumption of purified water, and also in case of an accident with leakage from the on-board urea tank it can easily contaminate water courses nearby, including underground waters.

Winter time is also critical for Diesel operators, since EGR-equipped vehicles have harsher start-ups and take a longer time to get a stable idling speed, which increases the particulate matter emissions due to the longer cold-phase after the start-up. The SCR is also a source of problems, since the urea-based fluid is easily prone to freezing due to the 67,5% water content.

EPA sucks, Diesel rocks

Yesterday, some bad news for the Diesel scene came out, because H&S Performance suspended the production of its tuning devices, including EGR/DPF delete kits. The company, currently a worldwide leader in the Diesel performance market, is now seeking for an EPA compliance to upcoming products.

Ironically, all that emissions control devices currently mandated by the EPA environazis such as EGR, DPF and DEF (urea injection at the exhaust, also known as SCR) have some side-effects. EGR decreases the fuel-efficiency and leads to a higher particulate matter amount, requiring more DPF regeneration cycles which also spend more Diesel fuel. Then, more energy is spent from the oil extraction to the Diesel fuel transport to the refuelling stations, going thru the refining. The extra components added to the vehicles, from the EGR to the urea injection setup, are pointless too due to the incresement in the raw materials amount demanded to make each vehicle. It's not really an effective way to cut emissions after all.

Performance-wise, the EGR prejudices the turbocharging effectiveness due to a reduction on the exhaust housing pressure. It's worth to remember the turbocharger also leads to a higher fuel-efficiency, due to the higher air intake flow promoting a more complete combustion process.

The increasingly common SCR/urea injection is also not so great as it's often quoted, since it demands more industrial processes to manufacture the industrial urea and a higher water consumption to make the standardized urea-based Diesel Exhaust Fluid, not to disconsider the increased complexity to the logistic procedures required to make it nationwide available.

EPA and its pointless witch-hunting against Diesel clearly show that environmental protection is not a real priority for the Diesel-bashing environazis.

Diesels: energy-efficiency doesn't need excessive complexity

For a long time, Diesel has been the prevalent option for customers on the market for vehicles with a lower fuel consumption. From the old irons like the Fiat 128 to the current offerings such as the Fiat Punto Evo, in spite of all the emissions control devices which led to controversial effects in reliability, maintenance schedules, and even in the so acclaimed fuel-efficiency, such as the EGR which re-routes part of the exhaust gases to the combustion chambers in order to decrease the internal temperatures to reduce the Nitrogen oxides generation, Diesel engines are still the easiest way to conciliate performance with fuel savings.

One threat to the Diesels' supremacy are the hybrids, such as the Toyota Prius, but don't seem to justify all that "eco-friendly" aura implied by the marketing. Delivering fuel-efficiency ratings very close, often worse, their manufacturing processes have an increased environmental impact, apart from the higher technical complexity. An average compact car, such as the Chevrolet Cruze, easily delivers a higher mileage in Diesel versions.

Comparing to a gasoline-powered engine which would provide a close performance, Diesel has been less complicated, mainly due to the absence of an electric ignition system. Older ones, with a fully-mechanical injection setup, are able to remain running even after an eventual alternator failure...

Altough nowadays electronic fuel injections became prevalent, mainly due to the higher adaptability to environmental factors which influence the performance and efficiency, Diesels remain less complicated that any gasser.

Needless to say how simpler they are comparing to the hybrids with all the complex integration between both primary (combustion) and secondary (electric) drive and the high-voltage components...

There were also some few attempts to conciliate the higher thermal efficiency of Diesel engines with Hybrid drivelines, such as the Peugeot 3008 Hybrid4, but the overall cost still goes too high for the proposed improvements on the fuel savings, also becoming too opulent for a "world-saving" lurker, when some less expensive vehiches with close functionalities, such as the Peugeot 308 1.6HDI, can provide a lower overall life ownership cost from the first registration to the final disposal or a life-extending refurbishment...

Hybrid-electric cars: a pointless marketing deal

Highlited as an alternative to cut tailpipe emissions, hybrid-electric vehiches are often pointed to have a lower operational cost, altough in this matter they're not so great at all. Considering the initial cost, a Chevrolet Sonic can be as cost-effective at the long run as a Chevrolet Volt, which can become around 150% more expensive competitively-equipped. After a predictable 10-year lifespan, it's still cheaper to just overhaul the engine of a subcompact than to overhaul the engine AND replace the traction battery packs of a hybrid...

Diesel-powered vehicles, spotting the Volkswagen Jetta TDI as one of the most successful in the American market, are also a cost-effective option. In spite of the higher cost, altough still around 35% cheaper than a competitively-equipped Chevy Volt, a Jetta TDI offers an easier adaptability to run on alternative fuels, which leads to a lower environmental impact without sacrifices to performance or driveability. Also considering the manufacturing of the traction battery packs and their end-of-life reprocessing, which lead to a high energy expense, easily overcome the energy-saving thru a predictable 10-year lifespan, that can be easily surpassed by a Diesel while a battery hardly lasts more than 7 years. It's also worth to note that nowadays in some markets even sportscars, such as the Audi TT, can be had with a Diesel, joining the higher fuel-efficiency with the weight-savings and enhanced aerodynamics, leading to more increasements in the fuel-efficiency and environmental performance...

After all, a gasoline-powered hybrid is essentially matter of foolish marketing...

Single windscreen wipers: nice or rice?

One of the most controversial features in street cars, altough greatly popular in race cars, are the single windscreen wipers. Used in low-cost cars like the early Fiat Uno, and also in some higher-end models such as many Mercedes-Benz vehicles from the 90's, it's often regarded as an undesirable feature.

In opposition to a widespread myth, which reports single wipers to prejudice visibility, they're widely used in race cars due to their benefits in this aspect: since the driver's seat is usually lower than in a street car, an average dual-wiper setup sits too high and ends up reducing the driver's visibility, while with a single wiper set to rest either standing in the middle of the windshield or laying in the passenger side, the prejudices are minimized. Also, due to the wider sweeping pattern, it can wipe more efficiently and cover a bigger portion of the windshield.

It's worth to note that, with a dual-wiper setup, which usually sweeps from the passenger side to driver's side, is that it dumps water right in the driver's field of view before it's cleared off...

Other features favorable to single-wipers are the lower weight, altough it doesn't look so significant at a first sight, and an improvement to the aerodynamics since it's one less thing to get dragging when the vehicle runs.

Then, in a racing environment it's desirable for performance while in a street car it helps to decrease fuel consumption at the long-term operation.

So, despite the occasional criticism from the haters, who quote single-wipers as a ricers' deal, it has some undeniable practical purposes in street cars...