From physical property measurement to modelling pore-scale environments, the study of fluids at the microscale is key to understanding and optimizing fluids for large-scale energy applications. Silicon-glass microfluidics is now a proven technology for chemical effectiveness testing in the conventional oil and gas energy sector. We see potential to apply microfluidic fluid characterization technology to renewable sectors, such as geothermal and solar thermal energy recovery where fluid customization is central to performance. Key to unlocking performance gains in these renewable energy systems are phase change material slurries (PCSs)-fluids that exhibit a high apparent specific heat capacity. However, testing PCS synthesis recipes is currently a slow and expensive process, given the challenges of dynamic testing at process-relevant temperatures and pressures. In this work, we develop and test a robust silicon microfluidic device and measure important PCS emulsion properties including (i) viscosity, (ii) shear stability, (iii) phase change temperature/hysteresis, and (iv) phase change stability under dynamic conditions where tests are performed quickly (<1 h) and require only minimal test fluid volumes.