Thermal Energy Storage (TES)
The need for thermal energy storage alongside electrical storage
To meet the needs of large-scale renewable energy deployment cost-effective energy storage systems must be put into place to overcome the variability in output from renewable energy sources. It is estimated that the energy storage capacity in the United States will climb from 23 GW in 2021, to 132 GW of storage by 2050 to meet the daily/diurnal demands of customers connected to the electrical grid.
While bulk utility-scale storage is seen as one way to address capacity requirements, a distributed model will help to alleviate the cost and energy demands required for grid operators to cost-effectively supply energy.
In a distributed model, wherein the customer manages a percentage of their energy storage, the systems they use are primarily broken down into two major categories, electrical and thermal. Electrical systems utilize various technologies to store electrons for later reuse, whether it be in the form of lead-acid batteries, Li-ion batteries, etc. Thermal Energy Storage (TES) systems store thermal energy in the form of sensible or latent heat. The focus of our existing work is the latter, wherein we utilize Phase Change Materials (PCM) to capture, store, and release latent heat via a first-order phase transition.
Phase change materials
In seeking out the best PCM’s we have explored the use of the three major categories associated with PCM’s; Salt-Hydrate (Inorganic), Organic (Bio), and Eutectics. Having tested various formulations of PCM’s we chose to work in conjunction with the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) to co-create a low-cost, highly energy-dense, easily manufacturable, and ecologically sustainable PCM that operates in an ambient temperature range. This chemistry has enabled us to develop our first-generation TES product for use in commercial HVAC (Heating Ventilation and Air Conditioning) applications - called the Melink T-Bank™. The development of the T-Bank was funded in part by the DOE Office of Energy Efficiency and Renewable Energy (EERE), under an SBIR Grant . The performance and characteristics of T-Bank have been validated by the University of Dayton (UD) and ORNL teams, and serve as the backbone from which this future work will be built upon.
For more about T-Bank, read about our full- and mid-scale test labs. For more about our PCM developments, read about our revolutionary phase change material Joule Juice™.
Why HVAC
Our focus on the HVAC market comes from our company's experience in the development of ventilation products and offering Test and Balance (T&B) services for commercial customers nationally starting in 1996. The desire to increase the energy efficiency of our customers led to the eventual establishment of a Renewable Services group in 2008 (now Melink Solar) and a Geothermal division Melink Geo in 2015 (now Melink ZERO). These developments have created a firm understanding of the benefits offered by renewable energy, and energy efficiency - something that we felt was lacking in existing HVAC solutions outside of Geothermal Heat Pumps.
Electrification of the grid
The introduction of TES alongside battery storage reduces the need for large-scale expenditures on utility grid reinforcements by balancing out the seasonal demand on the grid. The reduction in infrastructure expenditures by lowering or leveling the load required from the utility companies could eliminate the need for reliance on peaker plants, many of which are operated using natural gas as an energy source. The introduction of distributed energy storage in the form of electric batteries and TES would lower the kW demand from end-users. Alongside a utility-controlled cycling mechanism utilized during peak events, TES could further reduce the expense of operating larger power infrastructure and could lead to a reduction in end-users utility bills.
Cost-effective energy storage
Issue 10, 2021 of the journal Energy and Environmental Science published a paper wherein the model of Levelized Cost of Storage (LCOS) was used to perform a cost-benefit analysis on Li-ion and TES battery technologies, stating that “our LCOS analysis shows that in many situations, Thermal Energy Storage (TES) can be more cost-effective for buildings than Li-ion batteries.”
In our internal analysis on the performance of battery-assisted HVAC in hydronic heat pump systems similar to the ones used in our building, we found that TES is ~20-40% more effective at meeting thermal loads vs Li-ion.
As a manufacturer and service provider in the commercial building industry, we have observed that in the United States cost is a primary driver behind the decision-making processes of property owners, managers, and operators. Therefore, in our desire to develop a commercially viable TES system, cost is critical relative to its marketability and salability.
Introducing a revolutionary phase change material
To take the most advantage of thermal energy storage systems, we have participated in the development of a revolutionary new phase change material, Joule Juice™. Joule Juice changes phase at ambient temperature, with a narrow supercooling/subcooling band, making it the first PCM that can handle both heating and cooling in one TES system installation. Read more about our large- and mid-scale test labs.