A smart energy solution

[ggirod]

Living in the far north (well the far north of the USA, anyway - I am still a wuss compared to my brethren in Manitoba or, Brrrr! the Yukon ) I pondered as I contemplated my retirement house that I could freeze enough ice in the winter here to cool my house all summer. Free air conditioning! I just needed to make a very well insulated ice cube by exposing a block of water to the chill of winter until it froze clean through. Then insulate it from the warmth of the other season and in the summer, I would have lots of chilled water to cool my house.

Fortunately, careful energy design, extra insulation, natural sun shade from deciduous trees, and energy saving windows reduced my cooling costs to such an extent that my good sense could not justify that big block of ice. But, I was impressed with how little water was actually required and how that low tech solution could actually work. Enough of my amateur thermal engineering. What follows is really being implemented!

A California utility is deploying an energy storage solution to save peak power usage and move that usage to the nights when lots of cheap power is available. In short, they use a water reservoir that the company Ice Energy provides. All night, when temps outside are cooler and surplus power is available, they freeze the water into ice. The refrigeration system, working into cooler night time temperatures is much more efficient. Then, during the day when most air conditioners struggle mightily to cool buildings in the heat of the day, they use the ice to cool the building. In fact, by my calculation, the 450 gallons of water frozen over night stores around 3.6 million BTUs, or, if you like, 300 tons of refrigeration. They will pay for the installations simply with fuel savings over 20 years. They will also avoid buying lots of expensive on-peak energy and produce lots of cheaper off peak energy for sale.

Did you notice that no subsidy was needed? Well, this solution is so compelling that with today's cost structure it pays back. With tomorrow's it may be a real money maker.

Scientific American has an article on the system.

After seven years of development and testing, the Windsor, Colo.-based company signed an agreement recently with the Southern California Public Power Authority here to deploy some 6,000 Popsicle-making units at 1,500 locations in the utility's service territory around Los Angeles. Ice Energy says the units, called Ice Bears, will lead to a 30 percent fuel reduction for the utility through avoided use of so-called peaker generation plants, which are only turned on when demand is highest.

We can hope that more such simple solutions come to the fore and that companies and people can be smart enough to invest in them.

Methods to save energy present lots of relatively cheap solutions if the energy prices rise slowly enough and if people can invest wisely to adopt different ways of using energy. The operative idea is that the prices rise slowly enough.

I am posting this in news ... what follows is opinion ... read it if you like, skip it if you like.

I still believe that alternative energy solutions like wind, solar, and the others are also needed and we may need to bite the bullet and develop them before they are justified, because if we don't have them when they finally are cost justified, we will be in a big heap of hurt. When peak cheap energy (not just oil, Peak Cheap Energy) hits, prices will rise quickly and all of the low hanging fruit of conservation and thermal engineering like the idea above will already be in use. It will be too late then to deal with investing in alternatives.

[c1ue]

Re: A smart energy solution

It is a good - though not new idea - but I would point out that it is debatable just how much energy usage is reduced.

For one thing, maintaining ice blocks also means leakage: heat leaking in.

The principal difference would seem to be one rather of the cost of peak vs. off-peak power as opposed to significant overall energy use reduction: peak vs. off peak power is 2x or more different in cost while temperature differentials between night and day are only 15% on the Kelvin scale.

The result is still useful, but the benefits appear to be more load balancing than energy conservation.

[ggirod]

Re: A smart energy solution

The result is still useful, but the benefits appear to be more load balancing than energy conservation.

You are right, however, given our current situation, load balancing and reduction of peak energy usage is a savings because peak loading is accommodated with more expensive energy sources. To the extent that we can cope with both variable loads and variable sources we can harvest a lot more energy from our current and alternative sources. Imagine using off peak wind power to make ice .. for example.

Also, from the article, to the extent that the nighttime temperature is more than 15 degrees below the daytime, there is actual energy savings. In Southern California, the differential is considerably greater. So there are actual energy savings, though, I suspect, the peak/night electric rate savings justify the technology and the energy savings are just gravy for the shareholders and the planet.

[rshimada]

Re: A smart energy solution

After looking at the Ice Energy web site, I agree with c1ue: Ice Bear is about load balancing.

An Ice Bear has 450 gallons of water that provides around 6 hours of cooling, so that's 75 gallons of water for each hour of cooling.

I think it's likely that the Ice Bear compressor needs to run every night to freeze any ice melted during the day.

[ggirod]

Re: A smart energy solution

I think it's likely that the Ice Bear compressor needs to run every night to freeze any ice melted during the day.

Yes, indeed it does. However, running at night it pumps heat out to a much cooler night air temperature reservoir that CAN save some energy. Remember the efficiency of a heat pump is related to its input and output temperatures, so the cooler the night temp the better it does. So, mostly it is a load balancer but it also can save energy to the extent that the night temperature is significantly lower than the daytime temperature.

Given the heat storage of water vapor (really high humidity with elevated dew points) in southern areas other than California, for example Atlanta, the day/night temperature difference is much less than the 15+ degrees in California, and the technology would revert to purely load balancing. For dry climates with low nighttime temperatures, or even, maybe, with geothermal heat sinks (I haven't done the calculaions but suspect it might save energy) it is a savings.

Even as a load balancer it makes a major contribution. Nukes require steady loads, so this night time load is a benefit for nuke plants. Hydro ditto. Peaking sources are often not as efficient as continuous sources but are justified because of the peak demand... the less you have to peak, the less inefficiency you have to accept.

Air conditioning is a major seemingly unavoidable consumer of energy and it will probably increase over the years ... so anything that reduces its consumption is a good thing.

[Rajiv]

Re: A smart energy solution

Two other methods along the same lines

Natural production, storage, and utilization of ice in deep ponds for summer air conditioning

Abstract

A covered ice pond was analysed for the gradual production, storage, and utilization of ice for air conditioning of a building with an annual cooling demand of 1.2 TJ. Winter ambient air, blown into the pond for ice production, provided the major sources of coolness. The ice production rate and the total height of ice which can be produced were determined. The total heat gain by the ice pond was estimated by a two-dimensional heat conduction analysis, employing a finite difference technique. A coolness recovery factor of 0.84 and a coolness utilization factor of 23 were obtained for the system. An economic analysis showed that both initial and operating costs of the system are lower than those of a vapor compression refrigeration machine of comparable capacity.

Also - Stored Snow for Summer Cooling

Sundsvall Hospital is cooled by a snow bank of about 60,000 cubic meters.

Several Swedish companies are seeing business opportunities in the growing demand for district cooling systems. One of these, Snowpower, is taking a novel approach by using a simple raw material that’s found in abundance in northern Sweden: snow. The Snowpower system uses a 60,000 cubic meter pile of stored winter snow to cool the Sundsvall Hospital during the warmer months.

Like district heating, which is common throughout Sweden and many other countries, district cooling employs a network of pipes connected to multiple buildings or even an entire neighborhood. But instead of the warm water in a district heating system—often using waste heat or cogeneration from nearby industry—district cooling circulates water at a temperature lower than the ambient air. The source of chilled water is usually a lake or the sea, but that of course requires a waterfront location. District cooling is used in industrial process applications such as computer data centers, mines and power plants, as well as the more familiar air conditioning for personal comfort.

In 1990, about 10 percent of the cars on European roads were equipped with air conditioners, a figure that’s grown to nearly 90 percent today. And it’s not just in our cars that we’ve come to expect air conditioners; some form of comfort cooling is installed in an estimated 40 percent of all offices, hotels, hospitals, airports and shopping malls in Europe, and about 80 percent of similar structures in Japan and the United States. Today’s small-scale systems, where a compressor drives a refrigerant fluid, are not as energy-effective or environment-friendly as they might be (see sidebar).
District cooling offers a range of advantages for users, energy companies and society as a whole, for example:

• Lower emissions of greenhouse gasses
• Faster phase-out of ozone-depleting HCFC gasses as required by the international Montreal Protocol and many national laws
• Elimination of noise pollution from local compressors
• Improved esthetics (local compressors require storage rooms or sheds, and are seldom particularly attractive)
• Improved energy efficiency from larger systems
• Improved reliability with more centralized maintenance requirements

New life for an old technology

People have used snow and ice to keep cool in the summertime for centuries. As late as the early 1900s, businesses throughout Sweden would saw up blocks of ice from frozen lakes during the winter and stack them for storage under thick layers of sawdust. When summer came, horse-drawn wagons would make delivery rounds to local homes and businesses.

And there’s of course no shortage of snow and ice in the north of Europe. During a normal winter, Stockholm’s street clearing crews dump about a million cubic meters of snow in the city’s waterways, while across the Baltic in Russia, St. Petersburg tips as much as 25 million cubic meters into the Neva River. While a boon for motorists and pedestrians, this snow removal brings with it both logistical problems and environmental impacts, and both cities are looking into ways they can use snow for district cooling. Similar studies are underway in Turkey, Canada, Japan and other cities in Russia.

With the spread of electrification, refrigerators and freezers, the old ways of exploiting the winter freeze were largely forgotten. But by the 1970s researchers in Japan and the US were looking into using snow to cool indoor air. But water is a lot easier to cool with snow than air, says Kjell Skogsberg, the CEO for Snowpower who wrote a doctoral thesis on technical solutions for district cooling at the Luleå University of Technology (LTU) in Sweden’s far north.

The installation at Sundsvall Hospital is an important case for the study of district cooling. The basic principles are simple, with the snow bank stored near the hospital and insulated with a layer of wood chips. As the snow melts, the runoff water is filtered and pumped via a heat exchanger to hospital buildings. Then the warmed water is routed back to the snow bank to be chilled again.

The Sundsvall plant uses a combination of natural and artificial snow made by cannons. “The Sundsvall installation shows that the technology works and that we can save money by using snow for cooling,” Skogsberg explains. “The best approach, though, would be to have the snow stored in an underground bunker.”

Technical and environmental advantages




The diagram shows the design of the district cooling system at Sundsvall Hospital. CLICK FOR A LARGER IMAGE

Studies at LTU have looked at the environmental impacts of snow cooling systems compared with traditional approaches. The technology for snow cooling is simple: a lined pit in the ground is filled with winter snow and covered with an insulating layer. Melt water, just above the freezing temperature, is collected at the bottom, filtered and pumped via underground pipes to the customer.

Comparative studies show that the primary impacts from both snow cooling and traditional air conditioning systems occur during operation. Snow cooling is a clear winner, however, for its lower impact on climate, acidification and excess fertilization of waterways. Snow cooling requires more materials and much more ground surface area than compressor-based air conditioning to achieve the same effect, but a facility getting double use as a snow tip reduces this impact significantly. Air conditioning consumes much more energy than district cooling with snow.

[Starving Steve]

Re: A smart energy solution

One of the ways that California, for 50 years or more, has met its peak-hour energy demand is by producing power off-peak (during the night) and using that power to pump water up-hill from the California Aqueduct into the San Luis Reservoir near Los Banos, Cal. During peak-hour demand, the water generates power by flowing back down-hill and back into the California Aqueduct.

The Cal. Aqueduct channels water from Northern California to Southern Cal. This involves pumping the water up-hill 4000 feet over the Tejachipi Range and then down-hill into Southern Cal. Some of the energy for this pumping is stored in the San Luis Reservoir during the night.

Our parents thought big and engineered projects in a big way. They welcomed growth, welcomed people, and kept the cost of living low by engineering on a massive scale. The best example of this si se puede hacerlo approach is the California Water Project, opened half-a-century ago.

[GRG55]

Re: A smart energy solution

It is a good - though not new idea...

You are correct...this type of system has been around awhile. A hotel near Chicago that I used to stay at in the early 1990s had one of these systems. If I recall correctly at the time Illinois [or Chicago area] electricity prices were pretty steep and I think commercial and industrial users had contracts that benefited from off-peak vs peak consumption.

I remember this only because the system failed during a visit in July, and the hotel went to great lengths to answer guest questions about what had happened . Fortunately the ice makers in the bar kept working...

[ggirod]

Re: A smart energy solution

this type of system has been around awhile.

It seems many of the solutions like this are nothing but revivals of old techniques pulled out of the bag of tricks when economic conditions call for it. I remember really painful summer rate differentials in IL in the 80's because the utilities did not have enough capacity for peak demand in the summer. Companies instituted load management, rotating loads including building ventilation and cooling at the peak of the day and cutting demand by maybe 25-50%. Demand pricing led to manually implemented "smart grid" features. It may still be so, I left for a cooler climate.

Rajiv's article brought back thoughts of a byegone era when refrigeration was totally green and sustainable. In fact, if Kunstler's peak oil predictions come true, it may be so again. Here is a video of the process still being done to provide off-grid refrigeration.

[media][/media]

We can watch as more of this low hanging fruit is picked to make savings here and there. And, as in the ice cooled hotel, the marginal methods may be abandoned as soon as the prices drop again. Of course, one of these times the techniques will be adopted and not abandoned because the shortage will get worse. It is then that we will be forced to change. Will we be able to with the time and resources we have then?

[c1ue]

Re: A smart energy solution

Also, from the article, to the extent that the nighttime temperature is more than 15 degrees below the daytime, there is actual energy savings.

I was referring to 15% - a 30 degree Celsius day/night differential is only 15% difference in the Kelvin scale. And the Kelvin scale is what dictates energy use.

A coolness recovery factor of 0.84 and a coolness utilization factor of 23 were obtained for the system.

0.84 CRF would seem to imply a 16% loss. This in turn implies the Ice Bears system actually uses 19% MORE energy per unit of cooling. Coolness utilization factor - no clue what this is intended to represent. Certainly I cannot easily find a definition for this. Sounds like marketing speak.

Ice Energy says the units, called Ice Bears, will lead to a 30 percent fuel reduction for the utility through avoided use of so-called peaker generation plants, which are only turned on when demand is highest.

This additional energy use is likely not so much due to temperature differentials as it is due to startup costs for peaker generation plants. Still a load balancing issue.

You are correct...this type of system has been around awhile. A hotel near Chicago that I used to stay at in the early 1990s had one of these systems. If I recall correctly at the time Illinois [or Chicago area] electricity prices were pretty steep and I think commercial and industrial users had contracts that benefited from off-peak vs peak consumption.

Thanks for the tip.

I was actually referring to much older use: before the advent of the heat pump, people would 'make' ice by digging a deep cave, filling it with straw, then packing in snow during the winter. The further south, the deeper the cave.

Only works for the temperate zone though.

[GRG55]

Re: A smart energy solution

...Thanks for the tip.

I was actually referring to much older use: before the advent of the heat pump, people would 'make' ice by digging a deep cave, filling it with straw, then packing in snow during the winter. The further south, the deeper the cave.

Only works for the temperate zone though.

In Canada and the northern USA, before the widespread introduction of refrigerators, it was common to cut ice blocks from water bodies in the winter and then store them in pits packed in sawdust insulation for use in the icebox to keep milk and meat in the summer...

[thriftyandboringinohio]

Re: A smart energy solution

In Canada and the northern USA, before the widespread introduction of refrigerators, it was common to cut ice blocks from water bodies in the winter and then store them in pits packed in sawdust insulation for use in the icebox to keep milk and meat in the summer...

Yes, my father is old enough to have done that in rural Minnesota. He tells me they sawed ice blocks from the lake and put the blocks under sawdust in a corner of the barn and they would have useable ice through July.

[ggirod]

Re: A smart energy solution

Clue:

This additional energy use is likely not so much due to temperature differentials as it is due to startup costs for peaker generation plants. Still a load balancing issue.

Load balancing is non-trivial and, as the article points out, it is adequate cost justification for the systems.

Ice Energy says the units, called Ice Bears, will lead to a 30 percent fuel reduction for the utility through avoided use of so-called peaker generation plants, which are only turned on when demand is highest. ... The Southern California Public Power Authority paid about $100 million for the 6,000 units, a price that comes with a maintenance guarantee by Ice Energy ... That may seem pricey on its surface, but Ramirez insists the investment will save the utility as much as 20 percent in reduced fuel costs over a 20-year period.

But savings also accrue because making ice into a lower temperature reservoir at night is more efficient than during the heat of the day. The 15 F temperature difference is the energy neutral point so at >15F there is a savings; albeit probably not a lot.

Ice Energy seems intent on capitalizing on the same sort of simple system in the inverse, and Ramirez readily admits his technology applies best to warm climates. Energy is lost in the conversion process from ice back to water (as much as 15 percent), but Ramirez said a temperature gradient of 15 degrees Fahrenheit or more from day to night makes the product energy neutral.
"In most of California, the average gradient [the difference between day and night temperatures] is 22 degrees," Ramirez said. "We have a natural advantage provided by cooler temperatures to reject heat, instead of running the AC that has to overcome heat during the day."