Fuel Cell Waste Heat for Power and Pure Water

What is it about?

This research proposes a smart energy system combining a 5-kilowatt proton exchange membrane fuel cell (PEMFC)—which generates electricity from hydrogen with low emissions—and an absorption heat transformer (AHT) that upgrades waste heat to purify water. Fuel cells produce power efficiently but release low-grade heat (around 80-100°C) as a byproduct, often wasted. Here, that heat feeds the AHT, using a water-lithium bromide mixture to boost temperatures up to 98°C in the absorber, driving a distillation process for clean water. Simulations modeled the PEMFC's output: electricity peaks at 4.3 kW at 80°C, with usable heat from 1.7-2.1 kW above 85°C. Experiments on a real AHT setup (with plate exchangers and cooling tower) confirmed performance, achieving coefficients of performance (COP) up to 0.256—meaning 25% of input heat becomes useful output—and overall system efficiency of 0.571, 12% better than the fuel cell alone. Distilled water output ranged from 0.36 to 0.68 liters per hour, recycling absorber heat. Key tests varied fuel cell temps (85-88°C), showing higher heat loads increase water yield and efficiency. Unlike standalone fuel cells (efficiency ~50%), this cogeneration setup produces electricity, heat, and desalinated water simultaneously, ideal for remote areas or industries wasting heat (20-50% loss). Challenges include matching temps/pressures, but it proves viable at Mexico's Energy Research Center, promoting sustainable tech amid fossil fuel decline and water scarcity.

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Photo by Sam Balye on Unsplash

Photo by Sam Balye on Unsplash

Why is it important?

This study pioneers integrating a H2 cell with an Absorption Heat Transformer for tri-generation (power, heat, water), boosting efficiency 12% via waste-heat recycling—unlike prior FC-chiller pairings focused on cooling. Timely amid 2020s hydrogen economy push and water crises (2 billion lack access), it leverages low-grade heat (abundant in industries, 20-50% wasted) for desalination without extra fuel. Impact: Enables compact systems producing 4 kW power and 0.5 L/h water per unit, cutting emissions 10-20% in off-grid sites or refineries (payback <3 years at $5-11/MMBtu gas). Experimental validation guides prototypes, potentially scaling to GWs of clean energy/water, aiding SDGs in regions like Mexico with geothermal/solar synergies.

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