Powering Five Heavy Luffing Cranes Without Diesel: A Hybrid Battery and Flywheel Solution for Large Construction Sites

Customer Requirements

In this case study, a major UK contractor, in partnership with Zenobē and Dumarey Green Power, deployed a hybrid power solution combining PowerSkid second-life battery energy storage systems (BESS) and Peak Power 200 flywheels to power five Terex CTL-630 luffing-jib cranes. This innovative approach optimised battery size, reduced costs by over £750,000 per year, and achieved a 98% reduction in CO₂ emissions compared to traditional diesel generators. The case study showcases how Dumarey Green Power’s technologies can be integrated to deliver sustainable, high-performance power for construction sites.

The Terex CTL-630 Crane

The Terex CTL-630 is a heavy luffing-jib crane with a maximum lifting capacity of 32 tonnes. It features two primary electric motors – one for hoisting the load and one for luffing the boom, plus smaller motors for slewing. The crane’s peak power demand, accounting for simultaneous motor operation and high starting currents, is approximately 310kVA (263.5kW at a power factor of 0.85). Traditionally, each crane requires a 500kVA diesel generator to handle these peaks in power, leading to significant fuel consumption and emissions due to low average loads and idle losses.

Challenges with Diesel Generators

Tower cranes typically have low daily energy consumption (around 70–100kWh/day) but high peak power demands, making them challenging to power sustainably. Modern Stage V diesel generators struggle with low average loads, causing issues with diesel particulate filters (DPFs) and selective catalytic reduction (SCR) systems. To mitigate underloading, operators often use 100kW loadbanks, which consume excessive diesel and increase emissions. For the five cranes, this setup consumed approximately 2,400 litres of diesel per 70-hour workweek, emitting significant CO₂, NOx, and SOx.

Results

Before the hybrid system, each crane was powered by a 500kVA diesel generator with a 100kW loadbank to prevent underloading. This setup consumed 2,400 litres of diesel per 70-hour workweek across five cranes (480 litres/crane/week). Using the UK emissions factor for diesel (2.687 kg CO₂e/litre, 2023), the cranes emitted:

2,400 litres × 2.687kg CO₂e/litre=6,448.8kg CO₂e/week = 6.45 tCO₂e/week

Total emissions for five cranes were approximately 32.24 tCO₂e/week, with additional NOx and SOx from loadbank and idle losses.

With the BESS-flywheel system, each crane consumed approximately 100kWh/day, including 30kWh of parasitic losses (including flywheel operation, BESS cooling) and 70kWh for crane activity. For five cranes over a 5-day workweek (70 hours): 100kWh/day/crane × 5 days × 5 cranes = 2,500kWh/week

Using the UK grid emissions factor (0.207 kg CO₂e/kWh, 2023): 2,500 kWh/week×0.207 kg CO₂e/kWh=517.5 kg CO₂e/week=0.518 tCO₂e/week

Savings Achieved:

• Cost: At £0.24/kWh for mains electricity, the weekly energy cost was: 2,500 kWh/week x £0.24 = £600 per week
  Compared to £15,000/week for diesel (2,400 litres x 5 cranes x £1.25/litre, adjusted for 2025 fuel prices), this saved £14,400/week
• Emissions dropped from 32.24 tCO₂e/week to 0.518 tCO₂e/week, a 98.4% reduction (31.72 tCO₂e/week saved)
• Additional Savings: removing five 500kVA generators and loadbanks saved significant hire costs (estimated £2,000–£3,000/week). Combined with fuel and emissions savings, the site projects annual savings of approximately £750,000

Sustainability and Scalability

The use of second-life batteries reduced embodied emissions, while mains charging leveraged the UK’s decarbonising grid (projected to fall below 0.15kg CO₂e/kWh by 2030). For sites with renewable energy contracts, market-based emissions could approach 0kg CO₂e/kWh. For off-grid sites, pairing BESS with small Stage V generators could maintain low emissions.