I. Position of This Article and Its Assumptions
The terms microgrid and smart grid are already commonplace. However, there are not many discussions that rigorously describe what kind of control structure these systems adopt. In this article, we evaluate energy systems not by:
- whether the power source is “new” or “conventional,”
- whether it is environmentally friendly or ideologically appealing,
- whether it aligns with current policies or subsidy schemes,
but by a single criterion from the viewpoint of systems engineering:
“Is the system structurally stable, extensible, and reasonable to implement and operate?”
We explicitly avoid value judgments and idealistic arguments. We look only at the structural superiority or inferiority of the system.
II. Axes for Evaluating Energy Systems
When evaluating an energy system from an engineering standpoint, the following axes are important:
- Where are the control points located?
- Is system-wide synchronization assumed?
- How many external dependency variables exist?
- Are failures local or systemic when they occur?
- How much human intervention is required?
Energy “quantity” and “price” are only results. What determines those results is the control structure. Therefore, in what follows, we treat microgrids, smart grids, and off-grid systems as different control architectures and compare them on that basis.
III. Structural Characteristics of Microgrids
A microgrid is a mechanism for operating the generation, storage, and load facilities within a certain area as a local power system. In general, it is designed such that:
- under normal conditions, it is interconnected with the existing utility grid,
- when necessary, it disconnects from the main grid,
- and enters islanded (autonomous) operation.
The important point here is that a microgrid is built on the design idea of “switching between normal and emergency modes.”
Under normal conditions, it is synchronized with the central grid. Only in emergencies does it temporarily operate independently. From a regulatory or policy perspective, this is easy to understand.
However, when viewed purely as a control structure, this “normal–exception” assumption contains several structural contradictions.
IV. Structural Contradictions Inherent in Microgrids
1. The problem of synchronization as a premise
As long as a microgrid is synchronized with the main grid, the ultimate control of frequency, voltage, and supply–demand balance remains in the external central system. Islanded operation is only an exception handling mode, not the primary control regime for everyday operation.
In other words, “being capable of autonomous operation” and “being designed as an autonomous system” are different concepts. Microgrids often fulfill the former requirement, but not necessarily the latter.
2. The problem of scale and complexity
As the geographical or system scale of a microgrid expands:
- the number of control targets increases,
- interdependencies among components grow,
- and the optimization problem for overall control becomes more complex.
As a result, more advanced central control is required, and the structure tends to revert back to centralization. This is a classic trade-off seen in many distributed systems.
3. Non-technical boundary conditions
The boundaries of a microgrid are often defined by:
- administrative boundaries,
- business entities,
- or subsidy and policy schemes.
These are not necessarily based on technical optimality. This is a source of structural distortion in the system.
V. Vocabulary Issues Around Smart Grids and Smart Meters
In principle, smart grids and smart meters are technical concepts rooted in control theory and information theory. In public discourse, however, they are often used in much looser ways, such as:
- “smart grid = next-generation infrastructure,”
- “smart meter = advanced management device.”
Properly defined, a smart meter is an agent within a control system responsible for:
- measurement,
- communication,
- control.
In reality, however, many smart meters are operated merely as billing meters. This is not a matter of technical limitation. The meaning of the vocabulary has not expanded, but rather been diluted.
VI. Market Distortions Caused by “System-Wide Misunderstanding”
When discussions about control structure are omitted while devices, regulations, and subsidies are pushed forward, implementation tends to become locally optimized only. The result is:
- Individual components become more sophisticated.
- The overall control structure does not become simpler.
- System behavior under fault conditions becomes opaque.
This is not the fault of any single actor. It is a natural outcome of market formation without a shared design philosophy.
VI’. Verification Based on Observation and Implementation
The structural issues discussed so far are not hindsight theorizing. As early as 2010, our company developed and shipped its own smart meter, and collected real-world data nationwide. This allowed us to observe:
- the temporal bias of electricity demand,
- actual responses to price signals,
- and the limits of central control for supply–demand balancing,
not as theory, but as empirical data. From this, we concluded that while smart meters and smart grids are effective as control elements, as long as you do not own your own primary power source, control will always be externally dependent.
Based on these observations, since 2011 we have been developing, manufacturing, and deploying off-grid systems that are autonomous, distributed, and asynchronous. Crucially, these off-grid systems are not just emergency equipment. They are continuously operated, and their operational data is fed back into the design process. In other words, our off-grid architecture is not derived from ideology or policy, but is the result of an engineering process of observation → verification → implementation → operation → redesign.
VII. Positioning Off-Grid
We define off-grid as follows:
Off-grid is an autonomous, distributed energy system that does not assume external synchronization or central control, and internalizes control within the system itself.
Its key characteristics are clear:
- Control points are clear and local.
- System-wide synchronization is not assumed.
- Faults remain local instead of propagating.
- System expansion is linearly scalable.
- Operation is relatively simple.
This is not a matter of ideology. It simply means that off-grid satisfies the structural conditions for a stable system.
VIII. Conclusion
Off-grid is not an “alternative” to microgrids or smart grids, nor is it a subordinate concept that exists only if those systems are realized. When we evaluate energy systems as control structures, we naturally arrive at the conclusion that the most stable and implementable architecture is one that:
- minimizes external dependence,
- is autonomous, distributed, and asynchronous,
- and can be completed as a local system.
Off-grid is not chosen for ideological reasons. It is the structure that remains when you pursue the optimal solution from a systems engineering standpoint.
In the next article, we will explain how this design principle has been implemented in practice: what components and control methods we selected, and how they came together as the technology stack behind Personal Energy®.