Batteryless energy harvesting systems enable a wide array of new sensing, computation, and communication platforms untethered by power delivery or battery maintenance demands. Energy harvesters charge a buffer capacitor from an unreliable environmental source until enough energy is stored to guarantee a burst of operation despite changes in power input. Current platforms use a fixed-size buffer chosen at design time to meet constraints on charge time or application longevity, but static energy buffers are a poor fit for the highly volatile power sources found in real-world deployments: fixed buffers waste energy both as heat when they reach capacity during a power surplus and as leakage when they fail to charge the system during a power deficit. To maximize batteryless system performance in the face of highly dynamic input power, we propose REACT: a responsive buffering circuit which varies total capacitance according to net input power. REACT uses a variable capacitor bank to expand capacitance to capture incoming energy during a power surplus and reconfigures internal capacitors to reclaim additional energy from each capacitor as power input falls. Compared to fixed-capacity systems, REACT captures more energy, maximizes usable energy, and efficiently decouples system voltage from stored charge -- enabling low-power and high-performance designs previously limited by ambient power. Our evaluation on real-world platforms shows that REACT eliminates the tradeoff between responsiveness, efficiency, and longevity, increasing the energy available for useful work by an average 25.6% over static buffers optimized for reactivity and capacity, improving event responsiveness by an average 7.7x without sacrificing capacity, and enabling programmer directed longevity guarantees.

翻译：无电池能量采集系统摆脱了电力输送或电池维护的需求，能够支撑各类新型传感、计算与通信平台的运作。能量采集器从不可靠的环境源中为缓冲电容器充电，直到存储足够的能量以保证在电源输入变化时仍能维持突发工作。当前平台在设计阶段选用固定大小的缓冲器以满足充电时间或应用寿命的约束，但静态能量缓冲器难以适应实际部署中高度波动的电源：固定缓冲器在功率过剩时因达到容量上限而浪费能量（转化为热量），在功率不足时又因无法为系统充电导致能量泄漏。为在高度动态的输入功率下最大化无电池系统性能，我们提出REACT：一种响应式缓冲电路，能够根据净输入功率动态调节总电容。REACT采用可变电容组，在功率过剩时扩大电容以捕获输入能量，并在功率下降时重新配置内部电容器，从每个电容器中回收额外能量。与固定容量系统相比，REACT可捕获更多能量、最大化可用能量利用率，并有效解耦系统电压与存储电荷——从而突破此前受限于环境功率的低功耗与高性能设计。我们在实际平台上的评估表明，REACT消除了响应性、效率与寿命之间的权衡：相较于针对响应性和容量优化的静态缓冲区，REACT将可用于有效工作的能量平均提升25.6%，事件响应速度平均提升7.7倍且不牺牲容量，并支持编程者导向的寿命保障。