Ice Energy
A few weeks ago I attended a meeting for the Northern Colorado Renewable Energy Society in Fort Collins. The monthly meeting is held on the second Tuesday at 7:30 at The O'Dell Brewing Company on Lincoln Ave in Fort Collins. I found out about it because my friend Dan Bihn is a founding board member of the group and I was visiting his website and found the link to it.
I've always had an interest in energy as far back as I can remember. I recall my dad bringing home a small solar cell when I was about 10 years old and he used the light from a table lamp to run a small fan. I looked at it and asked with excitement if it would be possible to use the solar cell to run the table lamp and get free light as a result. Ahhh, I can still recall my first brush with perpetual motion/free energy. My dad laughed and said that wouldn't be possible because the amount of energy to run the fan was much, much smaller that what was required to run the table lamp.
Over the years, I became aware that most of the energy we use to support our modern lifestyles comes from fossil fuels. These fuels took millions of years to form and it looks like we are going to use them up in a small fraction of that time, possibly 200 years or less. In essence, we as a society are living off a rich inheritance when it comes to energy. So my curiosity about renewable energy is related to how we'll survive after those fuels are exhausted. So far, there doesn't seem to be a fuel that offers the economy, energy density, or convenience of fossil fuels like coal, oil, or natural gas. Because there are so many different producers involved, my guess is that the price will rise slowly, until the supply is nearly exhausted. In that regard, we'll run out of fossil fuels the same way rich people go broke, first gradually, then suddenly.
The speaker at the meeting was Gary Kaiser from Ice-Energy, a start up company in Windsor, Colorado that offers a way to store energy for cooling. Their product, called the Ice Bear, incorporates 3 main components: a storage tank, a heat exchanger, and a refrigeration management system. The storage tank is about 6 feet square and 5 feet tall that holds about 570 gallons of water as well as the refrigeration management system. Inside this tank are evaporator coils that are used to freeze the water at night when demand for electricity is low. Another set of coils contain a coolant that is pumped through a heat exchanger inside the building during the day to provide air conditioning. With this approach, the air conditioner doesn't need to run during peak demand hours.
The method used to freeze the ice is similar to that of a refrigerator. The Ice Bear requires a separate conventional compressor/evaporator refrigeration unit to freeze the water into ice. You may have heard of air conditioning units being sized according to their 'tons' of cooling. A ton of cooling is defined as capacity required to freeze a ton of water, which is about 250 gallons, into ice over a 24 hour period. Freezing one ton of ice in 24 hours requires about 12,000 BTU per hour to be removed from the water. A BTU is the amount of energy it takes to raise (or lower) a pound of water by 1 degree Fahrenheit. However, when water changes phase from liquid to solid, it takes 144 BTUs per pound to make that transition. A 570 gallon tank can hold about 2.3 tons of water. So just by changing the phase from ice to water or vice versa, the ice holds the equivalent of 650,000 BTUs of energy which is a large amount of energy to store. It would be equivalent to running a 12,000 BTU/hr air conditioner for 54 hours. Using an EER of 12, this represents about 55 KWh of electrical energy stored. To put it in perspective, that is equivalent to the amount of energy that can be stored in about 90 car batteries.
This image shows the components of Ice-Energy's system
I worked for an electric utility company one summer and they offered a device called a 'demand meter' that kept track of the maximum demand in addition to the cumulative total KW-h and would adjust the charge per KW-h depending on how high a demand the customer put on the system. They also offered a 'time of use meter' which allowed a customer to get a lower rate depending on when they used energy, charging higher rates during peak times of the day. There was even a type of meter that allowed the electric company to shut off the electricity remotely in the event that demand got too high. So utility companies aren't just concerned with overall energy usage, they are also concerned about peak usage and have several methods of providing incentives to level out the peaks.
The image shows the shifting of power consumption from day to night to level demand.
Since air conditioning is largely responsible for the peak power demand on hot days, it makes a lot of sense for the electric companies to get a provide incentive for their customers to use a storage device like an Ice Bear. This could help level demand between the day and night cycle that is seen during the warmer months. It would allow them to save costs by avoiding the high by reducing the peak loads and pass those savings on in the form of lower rates to those customers who would invest in a method to time-shift their energy demands.
I really got a lot out of the meeting and met some interesting people. I look forward to attending more of them in the future.
I've always had an interest in energy as far back as I can remember. I recall my dad bringing home a small solar cell when I was about 10 years old and he used the light from a table lamp to run a small fan. I looked at it and asked with excitement if it would be possible to use the solar cell to run the table lamp and get free light as a result. Ahhh, I can still recall my first brush with perpetual motion/free energy. My dad laughed and said that wouldn't be possible because the amount of energy to run the fan was much, much smaller that what was required to run the table lamp.
Over the years, I became aware that most of the energy we use to support our modern lifestyles comes from fossil fuels. These fuels took millions of years to form and it looks like we are going to use them up in a small fraction of that time, possibly 200 years or less. In essence, we as a society are living off a rich inheritance when it comes to energy. So my curiosity about renewable energy is related to how we'll survive after those fuels are exhausted. So far, there doesn't seem to be a fuel that offers the economy, energy density, or convenience of fossil fuels like coal, oil, or natural gas. Because there are so many different producers involved, my guess is that the price will rise slowly, until the supply is nearly exhausted. In that regard, we'll run out of fossil fuels the same way rich people go broke, first gradually, then suddenly.
The speaker at the meeting was Gary Kaiser from Ice-Energy, a start up company in Windsor, Colorado that offers a way to store energy for cooling. Their product, called the Ice Bear, incorporates 3 main components: a storage tank, a heat exchanger, and a refrigeration management system. The storage tank is about 6 feet square and 5 feet tall that holds about 570 gallons of water as well as the refrigeration management system. Inside this tank are evaporator coils that are used to freeze the water at night when demand for electricity is low. Another set of coils contain a coolant that is pumped through a heat exchanger inside the building during the day to provide air conditioning. With this approach, the air conditioner doesn't need to run during peak demand hours.
The method used to freeze the ice is similar to that of a refrigerator. The Ice Bear requires a separate conventional compressor/evaporator refrigeration unit to freeze the water into ice. You may have heard of air conditioning units being sized according to their 'tons' of cooling. A ton of cooling is defined as capacity required to freeze a ton of water, which is about 250 gallons, into ice over a 24 hour period. Freezing one ton of ice in 24 hours requires about 12,000 BTU per hour to be removed from the water. A BTU is the amount of energy it takes to raise (or lower) a pound of water by 1 degree Fahrenheit. However, when water changes phase from liquid to solid, it takes 144 BTUs per pound to make that transition. A 570 gallon tank can hold about 2.3 tons of water. So just by changing the phase from ice to water or vice versa, the ice holds the equivalent of 650,000 BTUs of energy which is a large amount of energy to store. It would be equivalent to running a 12,000 BTU/hr air conditioner for 54 hours. Using an EER of 12, this represents about 55 KWh of electrical energy stored. To put it in perspective, that is equivalent to the amount of energy that can be stored in about 90 car batteries.
This image shows the components of Ice-Energy's system
I worked for an electric utility company one summer and they offered a device called a 'demand meter' that kept track of the maximum demand in addition to the cumulative total KW-h and would adjust the charge per KW-h depending on how high a demand the customer put on the system. They also offered a 'time of use meter' which allowed a customer to get a lower rate depending on when they used energy, charging higher rates during peak times of the day. There was even a type of meter that allowed the electric company to shut off the electricity remotely in the event that demand got too high. So utility companies aren't just concerned with overall energy usage, they are also concerned about peak usage and have several methods of providing incentives to level out the peaks.
The image shows the shifting of power consumption from day to night to level demand.
Since air conditioning is largely responsible for the peak power demand on hot days, it makes a lot of sense for the electric companies to get a provide incentive for their customers to use a storage device like an Ice Bear. This could help level demand between the day and night cycle that is seen during the warmer months. It would allow them to save costs by avoiding the high by reducing the peak loads and pass those savings on in the form of lower rates to those customers who would invest in a method to time-shift their energy demands.
I really got a lot out of the meeting and met some interesting people. I look forward to attending more of them in the future.
Labels: energy
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