Energy Efficiency

I believe innovative technologies in Energy Efficiency, the fifth source of energy, that deliver a return on investment (ROI) of less than five years to their customers would have rapid market penetration and potentially greater returns on capital investments.  Unlike renewable energy technologies, successful Energy Efficiency technologies are far less constrained by Federal, State, or local ordinances and subsidies.  

I invented a novel wind turbine techonology ( see Wind Turbine Technolgoy: US Patents: 8,049,351 and 8,178,987) and reconfigured it and optimized it to enhance commercial cooling tower application by developing custom aerodynamic blades and a robust, stainless steel rotor structure: 


Patented Wind Turbine Technology: Gearless Rotor with Electric Generation at Rotor Perimeter Using Permanent Magnets and Stator System

A substantial portion of the annual electricity consumption in the United States is used for controlling and conditioning the environment of commercial facilities: Hotels, hospitals, convention and data centers, etc. It is estimated that some 100,000 large scale chillers and evaporative cooling HVAC systems are installed for this purpose in North America.  The vast majority of these installations are used well below their maximum capacity due to variations of the environmental conditions (seasonal, changes in relative humidity, and elevations) and type of facility and its occupancy.  Furthermore, many of these units have been installed a few decades ago and with little if any building automation controls.  Increasing the energy efficiency of these commercial HVAC systems would yield significant financial benefits to the owners together with a positive impact on the environment.  Energy efficiency is the low hanging fruit in the renewable market sector.

Commercial cooling towers and evaporative cooling units typically have six foot fans and larger that consume a great amount of electricity and eject high-energy exhaust air.  I have integrated the patented wind turbine with an air collection manifold to create the system shown below that can readily be installed atop a cooling tower or evaporative cooler to recover some of this exhaust energy at a far lower cost than adding sophisticated modern day control system for a large portion of the existing installed base.

          XT9000 System Retrofitted on Top of Typical Commercial Cooling Tower


The wind turbine in this application generates electricity when it is retrofitted to a cooling tower or an evaporative cooling unit, then that power is fed to the grid via a commercial grid-tie inverter.

A thermodynamic analysis of cooling towers produces a general governing equation that relates the water (L) to air (G) mass flow rates ratio to the hot-water temperature (T1) and cold-water temperature (T2) and the vapor mixture enthalpies as follows:

                                L/G = (h2-h1)/(T1-T2)                                                 

Where h2 is the enthalpy of air-water vapor mixture at the exhaust operation wet-bulb temperature and h1 is the enthatlpy of the air-water vapor mixture at the operating tower inlet wet-bulb temperature.  This cooling tower governing equation can be used to produce optimal tower cooling efficiency at a fixed tower water/gas mass transfer fill surface area for each ambient temperature and humidity and for a given fixed nstallation elevation.  Most cooling towers are of a specific design geometry and optimal energy consumption manangement can be controlled dynamically using sophisticated tower controls.  However, most installed cooling towers are over designed to meet such a wide range of general installation parameters and ambient variations that they are not used at full design capacity more than one percent during a typical operating year.  The XT-9000 retrofit system aims at reducing tower energy consumption by extracting energy from the exhaust waste air stream and without any further optimization of the water-to-air mass flow ration which can produce even additional and significant energy saveings.

A novel discovery was made during the development of this application, namely when the turbine is retrofitted to a cooling tower or an evaporative cooler, the cooling tower fan motor uses approximately 15-to-30% less energy.  The turbine power generation and the cooling tower’s fan motor power reduction was verified and certified by National Air Balance of San Francisco in accordance to the Associated Air Balance Council (AABC) testing and certification specifications. Thermodynamics dictates that when the turbine is installed atop these cooling towers the temperature of the cooling tower must rise.  Experiments on commercial cooling towers showed that this water temperature rise was less than a degree Fahrenheit that can be compensated for by slightly increasing the chiller exit temperature which further reduces the facility’s energy consumption.  The water temperature rise varies with the specific installation, the ambient conditions, the presence or lack of any controls and the optimal location of the turbine energy recovery system.  The over capacity design of these cooling towers to accommodate large variations in installation and operation variables makes this low cost energy savings application very attractive for the building owners.

Detailed financial analyses on numerous potential retrofit commercial sites show that the combination of energy generation and energy conservation of both cooling tower fan and chiller energy reduction from this installation yields significant savings in a facility’s energy costs.   A return on investment of less than five years can be realized before any Federal, State, or utility incentives.  This energy efficiency application combines energy generation and conservation together with environmental positive impacts (reduced carbon footprint) at positive and rapid economic returns.

A detailed ROI calculator was developed that combines the power generation from the turbine system, the power savings of the evaporator motor and the chiller as shown below.  This ROI calculator is used during the initial site assessment of this application to quickly determine the potential returns on the investment:  


Turbine Power Generated (kW) = 0.8

Evaporator Motor Power Saved (kW) = 5.5

Chiller Compressor Power Saved (kW) = 3.9

Total Power (kW) = 10.2

Duty Cycle (%) = 70

Annual Energy (kWh) = 62,493

Electricity Price ($) = 0.13

Annual Savings ($) = 8,124

Installed Cost ($) = 30,000

Total Incentives ($) = 0

Net Installed Cost ($) = 30,000

ROI (Years) = 3.7

The ROI Calculator shows a typical example of an application where the turbine generates 0.8 kW of power from the evaporator exhaust air.  In addition, the evaporator motor and the chiller consume 5.5 kW and 3.9 kW less respectively due to the turbine system retrofit.  The combination of energy generation and conservation totals some 10.2 kW that translates to 62,493 kWh per year at a duty cycle of 70%.  At a price of electricity of $0.13 per kWh the customer saves some $8,124 per year, which is an ROI of 3.7 years at an MSRP of $30,000 for the XT9000 without any Federal, State, or utility incentives.