Renewable Energy

By Gerald Robinson

Large private enterprises can play a significant role in deploying renewable energy technologies at scale while advancing their own financial and sustainability goals. A well-planned and executed strategy, backed by senior management, will achieve multiple benefits. Among these are utility cost reduction, "decarbonized" energy supply, disaster resilience, grid interoperability, employee-commuter cost savings, high levels of energy efficiency, water conservation, and reduced business risks associated with energy price volatility. Obtaining these benefits requires that renewable energy acquisitions be planned so as to exploit synergies with interrelated on-site infrastructure as well as Federal, state and region's energy, water and waste management conditions. Emerging technologies and practices offer opportunities for novel applications for power, heat, and gaseous fuels.

Applications

The following sections group renewable energy technologies and strategies into progressively cutting-edge categories.

Mainstream Technology

Solar PV – Today’s prices for solar photovoltaic systems demonstrate strong economies of scale making aggregated purchases across multiple sites attractive financially. Prices for large, >1 MW rooftop and ground mounted systems are at or below the $3.50/watt which equates to $0.09 - $0.11/kWh. Purchased Power Agreements for multi-megawatt offsite projects can offer significantly lower prices ($/kWh). Economies of scale are mostly achieved in customer acquisition and legal costs (Barbose, Weaver and Darghouth 2014; Honeyman et al. 2015). Sites with very low utility costs can be made viable through an aggregated procurement by leveraging economies of scale benefits.

Solar thermal (air and liquid) - Evacuated tube solar thermal technologies offer the ability to capture heat during sub-optimal weather conditions and can generate higher water temperatures than do flat plate collectors. This technology is also less orientation-sensitive and therefore easier to integrate into building facades. Solar walls and roofs are an effective technology for pre-heating ventilation air as well as night cooling, and are nearly maintenance free (Figure 1).

Figure 1. Solar thermal wall (Source: www.solarwall.com)

Wind - While it is often impractical to site wind projects onsite, power contract prices for large offsite wind contracts have fallen to below that of power from natural gas plants (Wiser et al. 2013). While small, building-mounted turbines have achieved some visibility and serve to make a certain “green statement”, given their size and siting constraints their contribution to overall energy needs is small.

Lifecycle-cost-effective

Ground source heat pump (GSHP) technologies exchange thermal energy with ground water or soil and provide an effective means of reducing purchased energy and water while providing an efficient, flexible, and low-cost means of capturing waste heat. GSHP systems require no cooling towers, saving on capital costs and space requirements, associated high water consumption and chemical treatment systems, as well as maintenance. They can serve a single facility but are most effective as part of a district energy system where waste heat can be easily utilized and where simultaneous heating and cooling is needed. High efficiency is achieved independent of climatic conditions, yielding five-to six-times more useful thermal energy than electric resistance heating.

Alternative fuels for fleet, vendor and employee vehicles are part of any comprehensive strategy. Establishing, for example, renewably-based vehicle chargers with one of the emerging vehicle-to-grid (V2G) approaches provides a means of enhancing resiliency, grid services (voltage support, power factor correction, VAR support), and reducing vehicle-related emissions and costs. Solar-PV-shaded carport structures are ideal locations for electric vehicle (EV) charging and or the implementation of V2G strategies allowing EV batteries and or plug-in electric vehicles batteries and engine/generators to provide load management services to nearby buildings and backup power capability during grid disruptions.

Emerging technologies and financing mechanisms

Building integrated solar PV (façade and window) or building integrated solar thermal technology (beyond thermal walls) developments represent an area of renewable energy of high potential currently receiving little industry attention. Intense market pressures to date have focused nearly all R&D investments on conventional roof, ground and carport systems.

Large energy users also have an opportunity to become active members of the project finance community, and to develop new and widely replicable financing mechanisms. One example is innovative power contracts such as the "synthetic power purchase agreements" (PPAs) used to a limited extent with wind and solar PV projects (Figure 2). Synthetic PPAs result in new-renewable generation being added to the regions’ transmission/distribution system without the constraints of gaining an interconnection agreement from merchant utilities. The generated power is not delivered to end-user; rather the customer pays a hedge price to the developer in exchange for the market price. This allows the developer to have a guaranteed price for power (the hedge price) and shares market risks with end use customer, which can see either income or an expense depending on the market price relative to the hedge price.