Calculating Energy Costs: Zeolite vs. Silica Gel
Vinesh k -
When we compare materials like zeolite and silica gel, most discussions revolve around adsorption capacity, lifespan, or cost per kilogram. But one factor often gets overlooked—and it’s one that can silently drain your budget over time: energy consumption during regeneration. Regeneration in this case means driving off the water that was captured to ensure that the material can be used again.
In many real-world applications, desiccants are repeatedly heated to drive off adsorbed moisture. This heating step adds up, especially across hundreds or thousands of cycles. So how much does it actually cost to regenerate 1 kg of desiccant over 1,000 cycles?
Let’s find out.
Zeolite 13X Heating Cost Estimate (1,000 Cycles at 275°C)
Assumptions:
- Mass of zeolite: 1 kg
- Temperature increase: 25°C to 275°C → ΔT = 250 K (regeneration temperature determined off of journals)
- Specific heat capacity: 943–1344 J/kg·K (sourced from journals)
- Heater power: 400 W (0.4 kW)
- Heater efficiency: ~60%
- Electricity cost: $0.1085 per kWh (Tempe Electricity Cost)
1. Energy Required per Cycle (Ideal):
Energy = c × m × ΔT
= (943 to 1344) × 1 × 250
= 235,750 to 336,000 J
= 0.23575 to 0.336 MJ (1MJ = 0.277778 kWh)
= 0.0655 to 0.0933 kWh
2. Adjusted for Heater Efficiency (Actual Energy Draw):
= 0.0655 to 0.0933 kWh ÷ 0.60
= 0.1091 to 0.1555 kWh
3. Cost per Cycle:
= 0.1091 to 0.1555 kWh × $0.1085
= $0.0118 to $0.0169
4. Total Cost for 1,000 Cycles:
= $0.0118 to $0.0169 × 1,000
= $11.80 to $16.90
Silica Gel Heating Cost Estimate (1,000 Cycles)
Assumptions:
- Mass of silica gel: 1 kg
- Temperature increase: 25°C to 77.5°C (ΔT = 52.5 K)
- Specific heat capacity: 800–1100 J/kg·K
- Heater power: 400 W (0.4 kW)
- Heater efficiency: ~60%
- Electricity cost: $0.1085 per kWh
1. Energy Required per Cycle (Ideal)
Energy = c × m × ΔT
= (800 to 1100) × 1 × 52.5
= 42,000 to 57,750 J
= 0.042 to 0.05775 MJ (1MJ = 0.277778 kWh)
= 0.0117 to 0.0160 kWh
2. Adjusted for Heater Efficiency
0.0117 to 0.0160 kWh ÷ 0.60
= 0.0195 to 0.0267 kWh
3. Cost per Cycle
0.0195 to 0.0267 kWh × $0.1085
= $0.00212 to $0.00290
4. Total Cost for 1,000 Cycles
$0.00212 to $0.00290 × 1,000
= $2.12 to $2.90
That was a lot of numbers—but one thing is clear: silica gel is nearly 5x cheaper than zeolite in terms of energy cost alone. However, this isn’t the whole story. While silica gel is cheaper to regenerate, zeolite can capture significantly more water per kilogram, potentially offsetting the higher energy expense.
In our next blog post, we’ll dive deeper into that tradeoff: Does zeolite’s superior adsorption capacity justify its higher regeneration cost? Stay tuned as we unpack which material truly delivers the best value per drop of water removed.