Hourly Matching: Stages of development of the decarbonization of power system

D-Sharing initiated hourly maching projects funded by the Government of Japan. The projects is developed based on the following analysis.

RE1.0-4.0
D-Sharing advocates its own theory of renewable energy development stages. In the Renewable Energy 1.0 stage, (1) there is almost no introduction of renewable energy in any time zone, (2) the introduction of renewable energy can be promoted in any time zone by stimulating the introduction of renewable energy on the supply side such as FIT, and (3) diversification is possible by differentiating preferential treatment for each type of power source.

In the "Renewable Energy 2.0" stage, (1) a certain amount of renewable energy is already being used due to FIT measures, (2) the demand side is stimulated under "real" renewable energy rules, and renewable energy is freely introduced through corporate PPA, etc., (3) as a result, investment is concentrated on solar power, which has the lowest installation costs, the carbon intensity imbalance between day and night is widening, and the gap between supply and demand can be adjusted. As a result, the carbon intensity imbalance between daytime and nighttime is expanding, making it difficult to adjust the supply-demand gap.

Renewable Energy 3.0 is a phase in which (1) 100% renewable energy is achieved during the daytime, but output shutdowns occur frequently, (2) the operating efficiency of thermal power generation declines, and (3) facilities deteriorate as base power sources are converted to regulated power sources. In this situation, we are at the stage of boosting the shift to renewable energy for all hours by stimulating the mutual tracking of supply and demand through a day shift in electricity consumption and a night shift in renewable energy generation, in order to stabilize the power system, lower electricity prices, and decarbonize the nighttime electricity supply. The background of this guidance review is that it is necessary to respond to the problems that will erupt during this phase.

In the "Renewable Energy 4.0" phase, 100% renewable energy power supply will be achieved in all time zones and all regions, and all customers will be stimulated to consume electricity from "real" renewable energy sources in all time zones. This is the stage where the supply side takes time-shift actions by installing storage batteries and developing nighttime renewable energy sources to achieve the same amount of renewable energy at the same time during all time periods, and synchronizes the energy consumption between the points as close to each other as possible. 

Hourly Electricity Generation by Source Type （Comparison　of　Tokyo Metropolitan Area and California, US）(Monday, March 20, 2023)

While Tokyo metropolitan area (TEPCO service area) generates less renewable energy based power than California, U.S., electricity peak demand comes mainly during the daytime, and the ratio of renewable energy to thermal power generation is relatively high due to the operation of solar power generation (Note that grid connection, pumped storage, and storage are not considered.)

As a result, in the Tokyo metropolitan grid, there exists a nearly 2-fold disparity between daytime and nighttime carbon intensity (g-CO2/kWh) while a 1.5-fold disparity in California. Similar trends are observed throughout Japan and in the eastern United States (PJM).

Comparison of Hourly Carbon Intensity　of Regional Grid（Monday, April 3, 2023）

5 Regional Grids (i.e., TEPCO, Kyushu Electric, CAISO, PJM and UK National Grid) are compared focusing on hourly Carbon Intensity (CI: CO2 Emission per 1kWh) on Monday, April 3, 2023 (local time).

TEPCO’s CI values are very high, exceeding 500g-CO2/kWh at its peak, followed by Kyushu, PJM, CAISO and UK National Grid. Except for PJM, however, CIs fluctuate widely between daytime and nighttime. In particular, CAISO’s peak CI is more than 350% of its lowest level. Although CIs of UK National Grid is low throughout the day, its peak is more than 150% of its lowest level.

 
Update of EBPM Framework for Zero-emission in Household Electricity Consumption

At RE 1.0, the carbon intensity (kG-CO2/kWh) is almost identical at any hour. Thus, reduction of power consumption was a sole activity which consumers should take, and an output indicator, ΔkWh is almost same as an output indicator, ΔkG-CO2,

In contrast, at RE 3.0, as the carbon intensity (kG-CO2/kWh) is considerably different by hours, in addition to power conservation shown as ΔkWh, activities are expected to make a time shift use to daytime when a higher ratio of renewable energy and relatively lower carbon intensity on the assumption that the volume of consumption is equal.

To monitor the actions under EBPM framework, the output indicator should be not only ΔkWh, but also the weighted average carbon intensity ((ΔkG-CO2/kWh)/year / consumer) for a certain period (e.g., year), unique for each consumer.

In other words, the reduction of CO2 emissions (kG-CO2) as an outcome can be appropriately obtained from the reduction of electricity consumption (kWh) as an output and the period/weighted average carbon intensity (kG-CO2/kWh) of each consumer.