thermal energy storage

Radiant Cooling Provides an Efficient Air-Conditioning Alternative

(3BL Media/Justmeans) - A sizeable portion (about 5%) of the electricity used in this country is used to produce air conditioning.  That translates into somewhere between 9 and 14 percent of the electricity used in homes and buildings. This has become a cause for concern on a warming planet, given that warming temperatures from energy generation will result in more air conditioning demand requiring more energy generation. This is otherwise known as a positive feedback loop. Some experts are even predicting that the need for air conditioning will exceed the need for heating by the end of this century.

A number of actions are being taken to begin to address this challenge, including, most recently, a move by the Obama administration to raise the standards for commercial air conditioning efficiency. Other innovations include the use of ice for thermal energy storage and evaporative cooling in hot dry climates, as well as continued, incremental improvements in conventional air conditioning systems based on the mechanical vapor-compression principle. While all of these are helpful, it’s not clear that any of them will substantially move the needle.

Another new type of cooling system called radiant cooling is beginning to attract attention in this country. Roughly half the net-zero energy buildings in this country use radiant cooling. The idea is that by cooling walls, ceilings, and floors, a draft-free, comfortable environment can be created. The cooling is produced as radiant heat from your body is absorbed by these cooler surfaces. Water can be used as the cooling fluid, for which it is far more effective than air. Radiant systems still move air for ventilation purposes, but far less air is required (only about 5% of the energy and 20% of the ductwork) for that purpose. That means smaller ductwork, and less fan power.

Radiant cooling systems have been popular in Europe for 25 years, but have been slow to catch on here. One reason why is that forced-air systems are less expensive out the outset, plus they require more space, making them a better fit for the US market. Now, with rising concerns over energy use, Americans are taking a second look, especially in larger commercial buildings where heating and cooling make up 40% of operating costs. They are especially useful in glass buildings that capture solar heat on tile floors. During summer months, cooling coils in the floor can draw that heat away.

Solar Desalination Solves Many Problems

(3BL Media/Justmeans) - It seems fitting, with World Water Week just behind us, and with news of the latest, even more dire assessment of the impacts of climate change from the IPCC still making the rounds, that we should share this story which shows one very effective way to connect the dots.

Given the changes coming down the climate pipeline, water is going to be an area of particular  concern, because we are so completely dependent on it to live, and because it’s going to be getting harder to find. Droughts are expected to increase. Snow melt, which often provides water in many regions for most of the year, is accelerating, often providing floods instead of nourishment, and changing rainfall patterns can deprive areas of water that previously had plenty.

Water and energy are inextricably linked. It takes lots of energy to pump water from one place to another and today’s thermal power plants with their cooling towers are among the nation’s largest consumers of water.

For all of these reasons, the announcement of a new solar desalination initiative is welcome news.

WaterFX is using a 377 foot-long solar array to turn brackish water, a mixture of fresh and salt water, into pure distilled water, also producing concentrated mineral salts as a byproduct. Brackish water is commonly found in estuaries, deltas and mangrove swamps, but it is becoming increasingly common as agricultural drainage as freshwater aquifers are depleted. This phenomenon is known as saltwater encroachment. It can also be expected to increase as sea level rises.

The Water FX technology, which has been dubbed “drought buster,” is currently being demonstrated in a $1 million project at the Panoche Water and Drainage District in Firebaugh, which serves the agriculturally rich Central Valley in California. Their Aqua4™ Concentrated Solar Still uses an approach that differs significantly from conventional desalination technology. Not only is it powered by the sun instead of electricity or other means, but it also relies on evaporation rather than reverse osmosis (RO) which is more commonly used. RO has been considered the more cost-effective approach due to the high energy cost associated with evaporation, but with the Concentrated Solar Still, the energy is free and clean. The rate at which fresh water can be recovered from salt or brackish water is also higher, as much as 93%, compared to 50% for RO systems. It also produces commercially desirable concentrated mineral salts as a byproduct.

A larger, commercial version of this plant, will be built later this year on 31 acres of land, capable of producing roughly two million gallons per day.

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