How Does Floating Head Pressure Reduce Energy Use?

Floating head pressure can save lots of energy and money.  Many people have heard this before but are hesitant to implement technology they may not understand.  If you need a basic understanding of how refrigeration systems and floating head pressure work, then read on. 

The Refrigeration Cycle:  Refrigeration is really all about removing heat and sending it elsewhere.  One or more compressors create pressure (and suction) which causes refrigerant to flow through a closed loop.  After leaving the compressor the refrigerant reaches a condenser coil (often on your roof) where it transforms from a gas to a liquid as it releases heat into the air.  The cooled liquid refrigerant then travels to the evaporator coils (in display cases and walk-ins) where it transforms from a liquid to a hot gas as it picks up heat and travels back to the compressor.  

Controlling Local Temperatures: When a local case or walk-in temperature rises above a specified threshold, a local expansion valve “opens” allowing refrigerant to flow through a local heat absorbing evaporator coil causing the local temperature to drop to the desired level.  Each case or walk-in can have a specific target temperature (not just medium or low temperature) to accommodate the grouping of products requiring similar storage temperatures as defined on their packaging.  Products having similar tolerances to defrost duration and frequency should also be grouped in cases.    

How Much Pressure Is Needed:  If all of your display cases and walk-ins were cold enough none of the expansion valves would be open.  Pressure in the closed loop system would quickly build up and the compressor motors would shut off after exceeding the specified “shut off head pressure”.  There needs to be enough pressure in the loop so that when one or more expansion valves open refrigerant flows.  There also needs to be enough pressure (and suction) to cause refrigerant to pass through the condenser coils at a flow rate which allows adequate release of heat into the air.  As outdoor temperatures decrease, each condenser coil’s ability to release heat into the air increases.  Colder outdoor temperatures also result in cooler refrigerant returning to the compressor.  This cooler refrigerant can absorb and carry more heat as it passes by evaporator coils.  As expansion valves open and close and outdoor temperatures rise and fall, the amount of (head) pressure required for correct refrigeration system operation goes up and down. 

Change System Pressure Based On Changing Needs:  Some refrigeration systems have you select fixed high and low (head) pressures which will determine when compressors start and stop enabling the refrigeration system to function properly, even under the most challenging conditions (all expansion valves open and the outdoor temperature is 112 degrees).  But what about when the conditions aren’t so challenging which is most of the time.  Maintaining high system pressure at times when it isn’t really needed means your compressor is running when is doesn’t have to.    Refrigeration system controllers can be added which change the shut off head pressure as outdoor temperatures go up and down.  This is floating head pressure.

Saving Energy And Money:  Floating head pressure saves energy by reducing the average amperage draw (motors perform less work when they maintain lower pressures) and compressor run time (cooler refrigerant allows target temperatures to be achieved sooner).          

Are Electric Car Charging Stations In Your Future?

What do Whole Foods, Meijer, Best Buy and the Mall Of America all have in common?  They have all implemented charging stations for electric vehicles in pilot locations.  Some charge a fee and others offer charging for free.  The free services are expected to decrease over time as the number of electric vehicles on the road increases.  It takes longer to charge a battery than it does to fill up with gas and customer cars spend regular amounts of time in retail parking lots.  As such, electric car charging stations are a natural fit for savvy grocers who want to be a destination for the growing number of people owning Chevy Volts and Nissan Leafs.  Most major cars companies have plans to release electric cars in the near future.

I envision covered parking areas featuring charging stations partially powered by solar panel roofs and maybe even a small wind turbine or two.  Solar panels and wind turbines can also be installed on your main building too.  If this sounds a bit too futuristic, keep in mind that the Department of Energy has been promoting new laws requiring some form of renewable energy on all commercial buildings.

If we don’t couple clean forms of energy with electric vehicles we will only be shifting carbon emissions from the tailpipe to the coal fired electricity generation plant.  By producing energy near the point of use we will keep in check the electric grid stress (and related distribution and upgrade costs) which will be created as vehicles shift from gasoline to electricity.

Wind Turbine Ideas

This post falls outside food retail energy efficiency but is very interesting.  Magnets and windings should be mounted on wheel shapes comprising the wing tip perimeter of wind turbines.  This will increase both generating capacity and electro-mechanical resistance.  By activating an increasing number of magnet/coil generation zones as wind power increases the generation of electricity can optimized across different wind speeds/powers.

Wind turbines will exist on the top of electric cars because the windshield creates a zone of dense high speed wind.  I imagine a cylinder shaped turbine embedded in the roof to shield the returning blades from the oncoming wind.  This will extend the range of electric cars and reduce battery stress.

An excellent place for wind farms are “pump storage projects”.  These large manmade elevated lakes near natural bodies of water were built in the fifties to help balance the power grids.  By pumping water up from the lower lake to the upper lake at night when the demand for energy is low this allows for the water to flow from the upper lake to the lower lake through an electricity generating turbine during the day when the demand for energy is high.  This is sort of like a giant capacitor.  Advantages include:

·        Turbines on top of an elevated lake can have shorter mounting towers

·        Wind at the top of the hill surrounding the manmade lake has greater density (wind power)

·        Pre-existing grid connections and power distribution towers

·        See http://www.visitludington.com/stories/ludington_pumped_storage_project

Food Retail Energy Efficiency - The Next Big Thing

People often ask me, "What's the best choice I can make to improve energy efficiency in my store?".  Over the years the answer to this question has been different ranging from night covers to T8 lighting to anti-sweat heater controls to ECM motors to LED lighting.  One common trend for food retailers is that the popular energy efficiency upgrades always have something to do with lighting or refrigeration...probably because these two items comprise the bulk of grocers electricity consumption.  It should not be a surprise then that retrofit door kits pre-fitted with LED lights installed on open multi-deck refrigerated display cases are the next big thing for food retailers.  The benefits are many:

Reduced compressor load and runtime - 50% reductions are common
Reduced lighting input power - 50% reductions are common
Easier lighting maintenance with vertical easy access fixtures replacing "hard to reach" horizontal fixtures
Enhanced merchandising from vertical door frame mounted LED lights shining directly on product facing
Reduced average product temperatures
Warmer aisles increasing customer linger time
Faster ROI for LED lights when combined with door packages - As fast as 18 months - 24 to 36 months is more common.

As with other leading edge energy efficiency solutions the technology is arriving before the prescriptive utility rebates do.  But for those who are ready to implement now, most utilities offer custom rebates which are typically larger than prescriptive rebates.  Reputable solution providers can help you with measurements and calculations which will qualify your upgrades for rebate dollars.  Another financial bonus (thanks to section 179 of the IRS tax code) is that you may be able to immediately write off 100% of the purchase price (up to two million dollars) as a tax deduction in the year the purchase was made.

Customer Choice for Electricity and Natural Gas

It’s hard to believe you can reduce your cost of electricity or natural gas with the stroke of a pen…but it’s absolutely true.  Here is what you need to know about getting the most out of customer choice utility programs.  These programs have been available in most industrialized states since 1999.  The idea is to introduce competition between electricity and natural gas utilities in an otherwise monopolistic business environment.  Even after you start buying energy from an alternate utility your local utility continues to provide distribution and other services without change.  This is because they charge separately for these services.  Just take a look at your utility bill and see the many separate charges.

You can buy electricity or natural gas directly from an alternate utility or you can buy from an agent who represents many alternate utilities.  I recommend the latter.  Here is why.  An independent agency is constantly monitoring the fluctuating energy prices and knows on any given day which alternate utility is offering the best deal.  An agent can make sure you are placed with a utility that does not have an early termination fee giving you the flexibility to switch to a different program when market conditions or the competitive landscape changes.  The point here is that each utility has its own unique pricing.  I recently switched a new single store customer of mine from one alternate utility to another alternate utility and dropped his price of natural gas by 21%.  

 Lastly, you should know that food retailers are highly desirable electric utility customers because of the large amount of energy used but more importantly the consistent pace of energy use stemming from refrigeration and lighting.  The latter means utilities won’t need to maintain as much extra generating capacity and distribution infrastructure like they do for customers who use a lot of energy once in a while.  If you have multiple locations, have your agent solicit custom bids from several alternate companies based on your total usage.  Customers who use lots of energy at a consistent pace are often granted the lowest rates…but only if you negotiate for them.

Polarized Refrigerant Oil Additives

Regarding polarized refrigerant oil additives.  I actually ran a four month field test measuring compressor energy consumption and weather conditions allowing me to normalize test results based on differences in temp and humidity over time.  The "treated" low temp system saved more energy than the medium temp "treated" system because oil viscosity in the low temp system caused oil fouling buildup to occur more rapidly.  Compressor energy reduced about 8%.  We also tested a stand-alone compressor group with the new poly oil refrigerant which everyone will need to go to eventually according to law.  This system showed no energy savings because the new refrigerants have a high PH value which results in the removal of oil fouling.  These new oils also have nano particles which improve the ability to transfer and carry heat (laminar flow) which compensated for the additive's secondary benefit of causing boil off to occur more aggressively which can improve heat exchange.  Bottom line:  PROA's work but not with the new refrigerants.