Hybrid Energy Systems

Diesel Generators Go Green—And Might Just Go Away Entirely

One hybrid solution reduces fuel, emissions, noise and service


For years, diesel generators have powered construction sites, supporting operation of everything from small hand tools and trailers to tower cranes and construction hoists. On large projects, that could mean bringing in dozens of generators. They’re essential but have many drawbacks.  

Generators burn considerable diesel and need frequent refueling, along with servicing about every 200 hours. They kick out noxious fumes and particulate matter that are damaging to the environment and unpleasant for workers. And their noise level ranges between 75 and 85 decibels—putting them somewhere between a hair dryer and a lawn mower. Worse, for most of the time, generators run inefficiently. 

But a new product, the POWR2 Hybrid Energy System (HES), mitigates these issues, promising a more fuel-efficient, eco-friendly and quiet solution that also extends service intervals. And as POWR2 builds out its fleet, it may also offer the potential to do away with generators entirely.  

Government spurs diesel generator clean-up for construction 

The HES includes three main parts: high-density lithium-ion phosphate batteries; industrial-grade inverters to convert the batteries’ DC power to AC; and an on-board controller. When the generator is running, any excess power recharges the batteries. During lower loads, the generator turns off and the HES switches seamlessly to battery storage—consuming no fuel and creating no noise. When the batteries are depleted or the load is greater than the HES can support, the generator restarts. 

Recharging is possible, because generators run at low loads 60% of the time. “You’ve got to specify a large generator to power a tower crane when it’s lifting its heaviest load and slewing at the same time,” said Tim Doling, global sales and business development director at POWR2. “But that happens just a few times a day. Much of the time, you’re just running electrical circuits and lighting systems. The generator’s sitting there, doing very little and running extremely inefficiently.” 

[RELATED: Will the Biden Administration Revive Home Geothermal? One Startup Thinks So.]

Although hybrid diesel generators and energy solutions became available in the United Kingdom more than a decade ago, the same market drivers—primarily government regulations and high fuel costs—weren’t issues in the United States. Then, the EPA put in place the Final Tier 4 standard, which called for generator engines to emit less particulate matter and lower levels of NOx, contributors to ground-level ozone. These are critical issues when running generators at low loads, which causes formation of soot due to poor combustion and low pressures and temperatures. Residues from unburnt fuel clog the piston rings, resulting in a further drop in efficiency. 

In addition to EPA regulations, utilities like Arizona Public Services are requiring a source of power other than a diesel combustion engine on their project sites. To provide cleaner options for temporary power, generator rental company Aggreko recently released a strategy to transition its fleet from diesel to gas, storage and renewables. These changes made a hybrid energy solution that can make the management of low loads much more appealing. 

The HES “brains” provide exceptional configurability 

The HES Energy Control Module (ECM) is the brains behind hybrid diesel generator operation. This on-board computer enables setup and control, selection of incoming charge current, displays the HES mode and feeds operational data to the cloud. Customers can sign into an online portal to monitor and control the HES remotely and respond quickly to any issues. The ECM provides alerts for out-of-range parameters, whether that’s low state of charge or overloaded circuits.  

The ECM proved critical on a project for the Federal Emergency Management Agency (FEMA). The agency wanted a solution to power temporary houses for evacuees in natural disasters. The power had to operate during the day but be silent from 8 p.m. to 8 a.m. And the equipment had to be password-protected so no one could adjust the controls.  

“We did a custom-designed program for the ECM that told the generator exactly when to start and stop,” Doling explained. “The ECM is very configurable to ensure it operates as the customer wants.” 

The  POWR2 Hybrid Energy System (HES).

Configurability also helps extend applications beyond construction.  

Before COVID-19, for instance, POWR2 provided HES units for events including the PGA Tour, golf’s preeminent series of annual tournaments. Generators are critical to operate large scoreboards, hospitality booths, concession stands and point-of-sale systems in the middle of a golf course with no power. But with players, spectators and TV crews also on the course, the smell and noise of a generator is unacceptable. Still, the PGA Tour might previously have had to run a generator 24 hours a day to avoid food spoilage and thawing. 

“We provided the HES and reduced runtime from 20 hours a day down to four hours a day,” Doling said. “The generator came on only to recharge the batteries.” 

Goodbye to the generator 

Even running a generator for hours may no longer be necessary. For now, POWR2 HES sizes start at 5 kVA and run to 90 kVA (90,000 watts). But in 2021, POWR2 hopes to launch a 100-MW model. 

“People have been accustomed to putting a small hybrid system or battery system next to a larger generator,” Doling said. “But we’re seeing a desire to flip that on its head.” 

Here’s how that might work for a tower crane. “Imagine you have a hybrid capable of taking the spike in the load,” Doling said. “The generator is much smaller and comes on only to charge the battery. So you can go from a megawatt generator to one a tenth of the size. Your emissions and all your costs associated with the generator are less.” For instance, you might power the tower crane with 1 MW of energy storage and top off batteries when needed by a 50-kW generator. 

That opens up another possibility. “Some construction sites have a grid connection, but not one large enough to support big motors for generators,” Doling said. “But if you have a battery system being charged by the grid, you can get rid of the generator altogether.” 

Of course, cost remains a factor. Doling noted that the HES runs double to triple the price of a diesel generator. “Although people initially get sticker shock, the total cost of ownership over the HES lifetime comes out less than a generator,” Doling said. “You don’t have to fuel it or service it every 200 hours. And the batteries themselves have a 10-year warranty. Even after 10 years, they still have 60% to 70% of their usable life left.”  

POWR2 primarily sells the HES to rental companies. But because HES is new technology, many customers want to try it first. For that, POWR2 owns a small rental fleet for those who want to make sure the benefits of reduced fuel, emissions, noise and smell are real.   

Modern Energy Grid

America needs a greener energy grid. What could that look like? 

Related Stories