• A two-site Philippine trial by DOCOMO, PLDT and Smart raised reported solar utilisation from 38% to 61%, a 23-percentage-point increase
  • Weather-linked control changes how battery capacity is divided between solar use and outage backup without establishing equivalent bill or outage reductions

The act

NTT DOCOMO said on 9 September that a trial with PLDT and Smart Communications at two Philippine base stations raised its reported solar-power utilisation measure from 38% to 61%, a 23-percentage-point increase. The sites were near Metro Manila and in Cebu and had different power-supply conditions.

The system combines solar generation, lithium-ion batteries and DOCOMO's energy-management platform. Using weather and electricity-demand forecasts, it adjusts how much battery capacity is available for routine charging and discharging and how much is kept in reserve for outages. DOCOMO said the control algorithm was redesigned for Philippine climate and power conditions.

DOCOMO first demonstrated the approach in Japan in 2016. Its earlier system had kept 80% of battery capacity in reserve to provide about 24 hours of backup, then introduced variable allocation based on weather forecasts. Those figures describe the Japanese deployment and are not specifications for the Philippine trial. The latest announcement reports improved solar utilisation but does not establish an equivalent reduction in electricity bills or customer outages.

The Assessment

The trial suggests operators may be able to get more use from batteries already installed at mobile sites, rather than adding more storage. If a large share of the battery is permanently kept for emergencies, that capacity cannot normally be used to store solar power for everyday operation. Adjusting the reserve when conditions allow can make more of the existing battery available.

The trade-off is resilience. The battery still needs to provide enough backup when grid power fails. Weather forecasts can help the controller decide when more capacity can be used during normal operation and when a larger reserve should be kept, but they cannot predict outages with certainty. The increase in solar utilisation is therefore more meaningful when it is reported alongside the amount of backup power the site continued to maintain.

For BTW readers, the control settings matter as much as the battery itself. A useful comparison would keep the required backup reserve the same, then measure solar use, grid consumption, battery cycling and performance during outages under each approach. That would show whether the system is making better use of existing storage without reducing the resilience expected from the base station.

What to watch

Watch for results showing minimum backup duration, forecast errors and performance during actual grid interruptions alongside solar utilisation. Results from more Philippine sites with different grid and weather conditions would show where flexible battery allocation can improve solar use while preserving the required communications reserve.