Lesson 14 – When TES Does NOT Make Sense: Engineering Boundaries and Red Flags
Lesson Purpose
This final lesson defines clear boundaries for using Thermal Energy Storage (TES), and highlights red flags that indicate when TES is not the right solution.
Good engineering is not about applying technologies everywhere — it is about knowing when not to use them.
Why This Lesson Matters
TES is often presented as:
- A universal energy solution
- A guaranteed cost saver
- A sustainability upgrade
In reality, TES is:
- Context-dependent
- Strategy-driven
- Unforgiving when misapplied
Understanding when TES does not make sense is a sign of engineering maturity.
Red Flag 1: No Clear Peak Problem
TES exists to address peak-related issues.
If a project:
- Has flat load profile
- Has no meaningful demand charges
- Operates mostly at steady load
Then TES solves no real problem.
Installing TES in such cases adds complexity without benefit.
Red Flag 2: Very Short Operating Hours
TES needs time flexibility.
If a building:
- Operates only a few hours per day
- Has short or insignificant peak duration
There is simply:
- Not enough off-peak time to charge storage
- Not enough peak time to justify discharge
TES becomes inefficient and unnecessary.
Red Flag 3: Poor ΔT Control History
TES depends heavily on ΔT discipline.
If a project or operator:
- Struggles to maintain ΔT
- Has unstable return temperatures
- Lacks flow control discipline
Then TES performance will degrade quickly.
TES amplifies existing weaknesses — it does not fix them.
Red Flag 4: Weak Operational Capability
TES is not a “set-and-forget” system.
If the project:
- Lacks trained operators
- Relies heavily on manual overrides
- Has unclear operational ownership
TES will eventually be bypassed, underused, or disabled.
This is not an operator failure — it is a system selection failure.
Red Flag 5: TES Selected for the Wrong Reason
Common wrong reasons include:
- “We have extra space”
- “TES looks innovative”
- “Another project used it”
- “It helps marketing or certification”
TES should never be selected to justify a concept.
The concept must justify TES.
A Simple Boundary Example
Consider a medium-size office building:
- Peak load: 500 TR
- Flat load profile
- No demand charges
- Stable grid supply
In this case:
- TES adds tanks, controls, and risk
- No meaningful economic return is achieved
- A well-designed conventional system performs better
Not using TES here is good engineering, not conservative thinking.
The Cost of Forcing TES
Forcing TES into unsuitable projects leads to:
- Underutilized storage
- Operator frustration
- Unexpected energy penalties
- Loss of confidence in the concept
This damages not only the project, but the reputation of TES as a strategy.
Engineering Judgment Perspective
Experienced engineers understand:
“A technology that works well in one project
can be the wrong choice in another.”
TES is powerful — but only within its proper boundaries.
Key Takeaways from This Lesson
- TES is not a universal solution
- Clear peak problems must exist
- ΔT and operational discipline are mandatory
- Weak operations are a major risk
- Saying “no TES” is often the correct decision
Final Reflection (Course-Level)
Before applying TES, always ask:
“What specific problem is TES solving in this project,
and what evidence supports that problem?”
If the answer is unclear, TES is not justified.
Course Conclusion
Thermal Energy Storage is not about tanks, ice, or diagrams.
It is about:
- Understanding load behavior
- Making time-based decisions
- Applying engineering judgment
This course was designed to build that mindset.