Getting to Net Zero Production: Part I
Given the climate emergency, getting to net zero in the production of entertainment events must be a top priority. This is the "first in a series of articles that maps a path to zero emission production of movies and live events.
Battery Energy Storage Systems (BESSs) are finding their way onto motion picture sets and live events. Primarily in the EU and British Isles, they have been used successfully on shows like The Witcher (Hungary), The Queen’s Gambit (Germany), and Heart of Stone (Portugal) to power the production’s catering, work trucks, 2nd Unit VFX, et cetera, but not the big show—set lighting. Powering set lighting remains the ultimate goal if we are to make it to net zero production.
I am here to say it is possible to power large set lighting and live event rigs with battery technology that is readily available today from equipment rental suppliers like Sunbelt, United Rentals, and Aggreko. While powering set lighting has proved difficult, recent developments in the design of BESSs now make it possible. It just takes an understanding of the limitations of the technology, how to overcome it, and the nature of the load to be powered. The reward is not only greener power, but also better-quality power. However, before we can begin to design a BESS for set lighting and live events, we must first know the capacity of a BESS.
What is the capacity of a BESS? It depends on the use application, involves some math, and is typically obscured in the marketing literature. The bottom line when designing a power system is how many amps we can draw per phase and for how long.
For diesel generators, ISO 8528 and ISO 3046 define ratings for Standby Power applications, Prime Power applications, Continuous Operation Power applications (COP), and Limited Time Running Power applications (LTP). Each rating represents a diesel genera- tor’s ability to support loads for each of these applications without overheating or being damaged. Since BESSs can be used in many of the same applications, and operating temperature also affects the performance of BESSs, some manufacturers give performance specifications for these same applications. It is important to understand these ratings when selecting a BESS for a particular application.
- Standby Power: A Standby rating is the maximum power available to power a load for only the duration of a power outage. While you will find a Standby rating in the product brochures of many BESSs, this rating does not apply to motion picture production or live events and should be ignored.
- Prime Power: A Prime Power rating is the maximum power available for unlimited hours (24/7 if required), provided that the load varies between 50% and 100% of the power source’s prime rating.
- Continuous Operation Power (COP): A COP rating is the maxmum power output that a power source can sustain for extended periods without overheating or experiencing significant performance degradation when the load is continuous.
- Limited Time Running (LTP): If the time under a continuous load is limited, the LTP rating can be used in place of the COP rating. An LTP rating refers to a power source’s maximum power output when a load is continuous but of a short duration. For example, a power source might have an LTP rating of 150% of the COP rating for 500 seconds, 200% for 50 seconds, and 300% for 10 seconds. This rating is used for applications where high power demands are occasional or intermittent
It’s essential to choose the right rating for a specific application to avoid overheating and equipment failure. For instance, choose the Prime rating for basecamp, the COP rating for set lighting, and the LTP rating for loads like the 70 kW Lightning Strikes fixtures. Using a power source beyond the designated rating for each of these use applications can lead to operational failure or damage.
Consider the POWR2 POWRBANK PRO 30.60/208. Like most manufacturers, POWR2 designates the inverter size in kW by first set of numbers in its model number. In this case, the inverter has a rating of 30 kW. The amount of storage capacity in kWh is designated by the second set of numbers (60 kWh.) The voltage is expressed by the third set of numbers (208 V, 3-Phase). The POWR2 POWRBANK PRO 30.60/208 would seem to have a capacity of 30 kW at 208 V 3-phase and last just under two hours under full load. However, in what application does it have a capacity of 30 kW? How many amps per phase is 30 kW? Answering those questions requires doing a little math.
The POWR2 POWRBANK PRO 30.60/208 has a capacity of 30 kW in Standby Power applications, or when used to power intermittent loads during power outages. Its Prime Power rating is less and depends on the ambient temperature (24 kW at 77°F and 22.2 kW at 104°F). POWR2 doesn’t give a COP rating in their product literature, but it is generally 80% of the Prime rating, which in this case would be 21 kW at 77°F.
You can see why it’s important to choose the right rating based on the use application. Using a power source beyond its designated rating can lead to overheating, reduced reliability, decreased lifespan, and potential safety hazards. While this is true for both diesel generators and BESSs, when designing a power system to be supplied by a BESS, the energy storage capacity of the BESS in kilowatt-hours is a major consideration since it determines how long the BESS will support the load before needing to be recharged.
When a BESS will be the sole source of power you must find its sweet spot, that balance between battery storage capacity and load demand that determines if the BESS will last a typical production day before it must be recharged. For example, on the Netflix show Irish Wish, the 30 kW/65 kWh BESS was piloted on a number of applications before finding success in powering the catering truck. It proved successful in powering the catering truck because the truck was only a 5-6 kW load. When piloted with larger loads, the battery ran down quickly, and the generator had to be brought back online frequently to recharge the battery. Only with loads under 6 kW to power more than just catering trucks requires augmenting their energy storage capacity.
Most BESSs can be ganged to increase their storage capacity and run time, but where in motion picture applications these units are typically mounted on trailers to make them mobile, operating multiple BESSs becomes an expensive proposition for production since each trailer will require another truck to tow it and another teamster to drive it. So, once you take into account the total operating costs (TOC) and the run time (a 30 kW BESS with a storage capacity of 60 kWh will last only a little under two hours under full load), most mobile BESSs are too small to be viable for large use applications and are really only suitable for side shows like catering trucks, crafty trailers, and port-a-potty trailers.
The big show
Powering a set poses a challenge because not only do large luminaires (18ks, 20ks, and Maxi Brutes) require more power than what most BESSs can support for very long, but also because of how we use these luminaires.
The motion picture industry does not benefit from “load diversity” when lighting sets. Load diversity is the concept that not all circuits in a distribution system are fully loaded and not all energized to full capacity at once. For example, the stage of a music festival has load diversity because lights come up and down on cue. The basecamp of a motion picture production has load diversity because a basecamp consists of multiple trailers with multiple heaters, air-conditioners, exhaust fans, refrigerators, microwaves, et cetera that cycle on and off. We can use Prime ratings, which are higher than COP ratings, in these use applications.
As the power log (Figure 4) of the current drawn by the Daddy’s Home 2 lodge set (Figure 3) illustrates, set lighting does not benefit from load diversity because it is continuous—once lights are turned on, they typically stay on for three hours or more.
Since set lighting does not %uctuate over time, the Prime rating for a BESS cannot be used when powering set lighting. Instead, we must use its significantly lower COP rating, or the maximum output that can be sustained continuously. Since COP ratings are typically 20% less than Prime ratings, this characteristic of set lighting has a big impact on the size of BESS required.
While a mobile 60 kW BESS with a Prime Power rating of 48 kW at 77°F (which translates to about a 133 A/phase) and a storage capacity of 120 kWh may be sufficient to power a small basecamp, it is not sufficient to power a set with the same peak load. That’s because basecamp loads are not on continuously for three hours or more, but instead cycle on and off. Since BESSs only generate power when called upon by a load, they last much longer when loads are intermittent.
To use a 60 kW/120 kWh BESS to light a set, requires we use its COP rating of 38.4 kW (about 106 A/phase)—which is not sufficient to power a set like the Daddy’s Home 2 lodge that draws 300 A/ phase. The continuous loads of set lighting will rip through the 120 kWh storage capacity of a 60 kW/120 kWh BESS much faster than the intermittent loads of a basecamp. So how do we power movie sets, like the Daddy’s Home 2 lodge.
Set lighting requires either a big BESS (like the 500 kW/1000 kWh “container” style pictured in Figure 6), or some means of combining the storage capacity and output of multiple smaller BESSs. Since increasing the storage capacity of a BESS also increases the time required to charge it, as well as its weight, paralleling the output and storage capacity of smaller, lighter BESSs that will charge quickly and are easy to transport is, in my opinion, the more viable option for set and live event stage lighting.
Until very recently, BESSs could only be daisy chained to increase storage capacity. Now some manufacturers of mobile BESSs are incorporating paralleling capability into their designs. Viridi uses a paralleling capable inverter by Sinexcel Electric in its 30 kW/150 kWh RPS 150 (pictured in Figure 7). POWR2 uses a separate paralleling controller, called POWRSYNC (pictured in Figure 8), that enables their mobile BESSs to operate in parallel, thereby increasing both storage and power output.
To power larger loads for a longer time, these grid-forming systems combine the ampacity of the individual BESSs while balancing the load between the BESSs by constantly monitoring load levels and automatically switching between the BESSs as they are depleted. The total ampacity of the resulting microgrid is dependent on the number and size of BESSs paralleled. How much power are they capable of? The common power bus of the POWR2 POWRSYNC is capable of up to 1000 A/phase—more than enough ampacity to power big setups like the exterior blue screen stage pictured in Figure 8. While the DEIF controller Viridi uses is capable of paralleling up to sixteen 30 kW BESSs for an ampacity of 1,333.92 A/Ph, for a total of 4,001.76 A—more than enough to power a warehouse stage. What about the run time?
With a useable storage capacity of 96 kWh before recharging is necessary, four paralleled POWR2 XPRO 60s can provide 384 kWh of stored energy. While not a lot for a motion picture set, hot-swap- ping depleted XPRO 60s for freshly charged ones will provide perpetual power. Since it takes little over three hours to charge an XPRO 60 from 20 to 99% on a 208 V 3-phase grid drop, they can be swapped out multiple times a day if necessary to assure continuous set power.
Now, small BESSs can be used as building blocks to construct clean mobile power systems that can be scaled up or down to meet the power demands of a show across the board—from the many small side-shows of a production to the big show as well. Capable of providing 106 A/leg 3-Phase, one POWR2 XPRO 60 can be used to power catering or an extras’ holding tent for example. Two can be paralleled to power a basecamp. If a production’s EV %eet is to be charged in basecamp, a third XPRO 60 can be added in parallel for a capacity of 318 A three-phase, while four in parallel, 424 A/leg, can be used to power a set. Up to 16 Viridi RPS 150s can be paralleled for a capacity of 1,478 A/leg to power a stage. In each use application, depleted batteries can be swapped out under load for freshly charged ones to provide perpetual power.
The value of having interchangeable small building blocks to meet all the power needs of a production cannot be overstated. Not only can it provide limitless uninterrupted power, it can also provide cost savings that come only with economies of scale and streamlining of battery management.
For example, rather than the added cost of an additional stake bed truck and additional Teamster driver to tow each of them, these BESSs are small enough to be forked on and off %at beds, making it possible for a production to use one “Moffet” style flatbed truck or trailer and one Teamster driver to transport multiple BESSs at once, at a huge cost savings. Small BESSs charge quickly and require less power to charge, making it easier to find charging locations.
While still not quite as turnkey a solution as diesel generators, the reward to using mobile BESSs is not only greener power, but also better-quality power that is safer and more reliable than that provided by diesel generators.