Archives for July 2019

VPPs with smart inverters offer crucial flexibility to the changing grid

July 11, 2019 By gk104 Leave a Comment

Energy generation and consumption is rapidly transforming into a decentralized, decarbonized, and digitized model due to a number of market forces. The declining costs of solar energy systems, as well as the increasing price of energy from the grid has led to grid parity. This has caused PV proliferation to accelerate to such an extent that in the past five years alone, PV installed capacity has increased by 300%. Simultaneously, the EV market is also on the rise and is expected to reach the electrification tipping point by 2030. This is due to support from governments trying to limit the effects of climate change, thus leading to automotive manufactures transitioning their fleets from standard petrol- and diesel-powered cars to EVs. As a result of the acceleration of both of these markets, EV charging has created demand patterns causing an even steeper and faster ramp-up in the evenings than the PV duck curve. , This is causing the grid’s balancing act to be increasingly complex. In order to support this new energy dynamic, advanced management software is required to ensure grid stabilization and to unlock the value of these energy resources.

Demand flexibility is a crucial element for a smart grid to leverage in order to maintain stability. Fortunately, the potential for behind-the-meter flexibility in the residential sector is particularly promising. A report by Wood Mackenzie found that there is currently ~47 GW of demand-side flexibility in the U.S residential sector alone, and it is forecasted to reach ~88 GW by 2023. This growth in demand flexibility could be in part due to PV incentive structures evolving towards self-consumption as it incentivizes system owners to consume more of the energy they produce. This is leading to consumers installing EV chargers, solar batteries, and other smart energy devices to better leverage the production of their PV systems. However, in order for these distributed energy resources to truly offer any value in terms of self-consumption and grid stability, they need to be smartly managed both locally and at the macro level.

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Key to managing these new flexible energy resources is the smart inverter, which acts as an energy manager for PV, storage, EV charging, and other smart appliances, in addition to grid interaction. At the local energy system level, the inverter can be programmed to maximize self-consumption, such as storing excess solar energy in a battery for later use or shifting consumption to match PV production. While at the grid level, the inverter can manage these underlying demand-flexible resources to support grid stability, such as discharging batteries into the grid to meet demand or pausing EV charging to decrease demand. Due to the inverter’s location as an interface between the local energy system and the grid, it also plays a strategic role in the deployment of virtual power plants (VPPs). VPPs pool PVs, batteries, and EV chargers in the cloud to instantly and automatically modify generation or consumption in order to stabilize grid frequency and voltage and more efficiently meet demand. Within the framework of VPPs, the inverter is responsible for disaggregating commands to underlying distributed energy resources (DERs). VPPs support three scenarios: meeting supply shortages, hedging pricing volatility, and maintaining grid stability. An example of a VPP meeting a supply shortage would be that in an area in which supply cannot meet demand, a utility is able to preschedule battery charging so that they can be discharged when needed, meaning substations do not surpass expected capacity.

One of the main reasons that VPPs are a promising new addition to the energy ecosystem is that they provide value to all stakeholders. System owners who participate in VPPs by allowing the utility access to their batteries or EV chargers, enjoy increased ROI for their systems either from upfront subsidies for hardware or from monthly rebate programs which grant the utility access to batteries and EV chargers. Energy suppliers also receive value with increased protection from price peaks, due to capped pricing that hedges against price volatility. This has the potential to save energy suppliers $30-80/kW per year. Lastly, Distribution Network Operators (DNOs) can defer building costly (~$10-20M) and often underutilized network infrastructure by leveraging pooled energy in VPPs to instantly overcome local supply shortages., By providing the flexibility to gradually increase storage capacity to meet a growing demand, VPPs eliminate the need for DNOs to purchase costly voltage regulator equipment, saving thousands of dollars per feeder.

Demonstrating their value and real-world capabilities, VPPs are already being deployed across the globe. For instance, SolarEdge has already worked with various utilities to deploy VPPs in different countries, such as the United States and Australia. In California, when a utility required load shedding for an ISO-triggered demand response event, SolarEdge provided VPP access to a fleet of residential storage systems. During this event, which lasted throughout three consecutive days, the VPP gave commands to all the connected storage systems in the area to charge batteries from the PV. Afterwards during a four-hour period each day, the batteries were discharged at a desired power and duration in order to provide power to the grid.

Another example of a VPP in action is when a Massachusetts’ utility required load shedding during three hours of peak demand. SolarEdge provided VPP access to a fleet of residential storage systems. During the load-shedding event, the batteries provided site-level energy supply with no grid export in order to match site load, meaning the homes were temporarily operating off-grid during this time. These applications show that as more PV systems and batteries are installed and help create a decentralized model of energy distribution, VPPs gain more access to more energy and thus their potential to support grid stability increases. However, the implementation of VPPs is only the first step for the smart grid. Combined with the power of artificial intelligence, machine learning, and data analytics, the technology behind VPPs will ultimately further evolve to make insight-driven decisions for optimizing energy allocation.

Virtual power plants and smart inverters are on the agenda for several educational sessions at DISTRIBUTECH 2020cvbbqaewbwzwrvrxfyaewxtxsybccdcfdtbev, set for San Antonio, Texas, January 28-30, 2020. See you there!

First published on 2019-07-11 13:09:30

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75 MW of community solar coming to Illinois in Ameren, ComEd territories

July 10, 2019 By gk104 Leave a Comment

Arlington, VA based Summit Ridge Energy (SRE) announced that it will acquire 11 projects from Pivot Energy in Illinois totaling 29 MWs, increasing SRE’s portfolio of community solar projects in the state to more than 20.

Pivot developed 29 MWs that won Adjustable Block awards, and will be contracted by SRE to handle customer acquisition and management for those projects.

“We have been fortunate to work with SRE on these projects, which are some of the first community solar arrays in the state,” said Pivot’s CEO, Rick Hunter. “Pivot is committed to our project communities and the Illinois market for the long run, and we’re glad to have a partner with the same mentality in SRE.”

Mark Raeder, SRE’s Principal in the Midwest, said the company plans to construct over 75 MWs of community solar in Illinois alone over the next 18 months. “We’re breaking ground on several projects in Ameren service territory this summer, with construction activities beginning in ComEd shortly thereafter. With favorable renewable energy legislation likely to pass in Springfield this fall, we’re continuing to acquire projects across the state, serving to further expand our presence and demonstrate our strong commitment to the Illinois market.”

“Both Summit Ridge and Pivot have been active in the Illinois market since well before the launch of the Adjustable Block Program,” said SRE CEO Steve Raeder. “Our funding vehicle, Summit Ridge Capital, coupled with Pivot’s customer aggregation platform, SunCentral, will enable thousands of customers to realize the financial benefits of community solar across Illinois.”

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The recent expansion of community solar programs across 20 states to date has become the catalyst to America’s commercial solar industry, presenting tremendous opportunity for customers who want the cost and environmental benefits of solar without installing panels on their roof. Community solar provides reduced electricity costs for consumers, regardless of their socioeconomic status or geographic location, protects the environment, and reduces our dependence on fossil fuels.

First published on 2019-07-10 14:23:23

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Driven by China, global investment in clean energy falls

July 10, 2019 By gk104 Leave a Comment

Gerald Porter Jr., Bloomberg

Worldwide investments in clean energy projects have hit a six-year low.

Global spending totaled $117.6 billion in the first half of 2019, down 14% from a year earlier and the least since 2013, according to a report by BloombergNEF. Investments slowed in all three major markets — the U.S., Europe and China — but China’s decline was especially pronounced as the country continued its shift away from subsidies for solar and wind power.

The slide in spending underscores how much sway China holds in the global market for renewable energy. Despite a 39% plunge in investments, the country remains by far the world’s biggest clean-energy spender with deals totaling $28.8 billion in the first half. Its decision to pull back subsidies was also the chief reason for a drop in global spending last year.

“The slowdown in investment in China is real,” said Justin Wu, head of BNEF’s Asia-Pacific region.

Some possible good news for the clean energy industry: Spending may pick back up in the second half of the year as an auction for solar power in China triggers a “rush” of project financing and some big offshore wind deals come through, Wu said.

Spending in some countries including Japan and India rose. And despite the drop in Europe, investments in both Spain and Sweden took off, jumping by more than 200% in both countries.

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First published on 2019-07-10 13:39:13

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The amorphous, heterogeneous spatial spread of Wolbachia

July 9, 2019 By gk104 Leave a Comment

Penelope A. Hancock presents recently published work on ‘Predicting the spatial dynamics of Wolbachia infections in Aedes aegypti arbovirus vector populations in heterogeneous landscapes‘.

Uncertainty surrounding density-dependent mosquito population growth rates prevents us from predicting the outcome of mosquito control interventions. A timely example is the introduction of Wolbachia bacterial infections into wild Aedes aegypti populations, the major vector of the dengue, Zika and chikungunya viruses. Wolbachia suppresses the ability of mosquitoes to transmit these viruses to humans. Once introduced, it spreads via a driving mechanism that allows the bacteria to infect a higher proportion of mosquitoes over successive generations of the mosquito population.

Field releases of Wolbachia into the wild Aedes aegypti populations in Cairns, northeast Australia, resulted in surprising patterns of spatial spread that were highly variable and difficult to predict. We developed a new mathematical model incorporating the results of experimental studies of density-dependent dynamics in this mosquito species. The model produces patterns of spatial spread that show similar features to those observed in the natural populations of Cairns (see animation below). Spatial spread is slow and amorphous, with the Wolbachia advancing further in some directions than others.

Variability is the norm

High variability in fundamental demographic traits, such as survival and fecundity, is characteristic in Aedes aegypti mosquito populations. Body size, as measured by wing length, shows a wide range of values over a typical sample of individuals collected from the field (Figure. 1A). This variation is important because body size is closely associated with fecundity in female mosquitoes, an essential parameter in models of mosquito populations and how they respond to interventions. Experiments conducted in field-caged mosquito populations show a close relationship between female body size, fecundity and the level of density-dependent competition that the mosquito experiences during its larval development stage (Fig. 1B). In addition, the time it takes for larvae to develop into adults is also strongly density dependent. This means that density-dependent dynamics need to be accounted for when predicting mosquito generation times, and in modelling the spread of Wolbachia from generation to generation.

Figure 1. A. Wing lengths of female mosquitoes sampled from the field and the field cage. B. Female fecundity (red) and larval development time (blue) resulting from different larval densities.Putting it all together

Our experimental studies of density-dependent demographic relationships have enabled the development of a mathematical model that represents variation in mosquito numbers across space and time. The model was able to produce patterns of spatial variation in mosquito abundance that are similar to those seen in field populations (Figure. 2A). We also found that the rates of spatial spread of Wolbachia predicted by the model were similar to those observed following the field releases conducted in northeast Australia (Figure. 2B). Our models can help interpret Wolbachia field release dynamics by allowing the effects of environmental and demographic heterogeneity to be considered.

Figure 2. A. The number of pupae per house, observed in the field and predicted by the model. B. The observed spread of Wolbachia at two sites in Cairns in comparison to the model prediction.

Read the full article, ‘Predicting the spatial dynamics of Wolbachia infections in Aedes aegypti arbovirus vector populations in heterogeneous landscapes‘ in Journal of Applied Ecology.

Photo by Kmaluhia

Positive effect of climate change on canopy trees does not translate to forests

July 8, 2019 By gk104 Leave a Comment

Yong Luo and colleagues recently had their paper published in Journal of Ecology. Read more about their work below.

Global change ecologists have often used trees under weak competition to examine relationships between climatic change and tree growth. Scaling up these results to a forest relies on the assumption that the climatic change-tree growth relationship is not affected by tree-level competition; especially the competition gradient from dominant trees to suppressed trees in a forest stand.

Read the full paper online: https://doi.org/10.1111/1365-2745.13228

By using permanent sample plot data from the central Canadian boreal forest region, where warming did not result in water deficit, Dr. Yong Luo and his colleagues found that growth increased over time for trees under weak competition, but decreased for those under strong competition. The divergent temporal trends among trees under different levels of competition led to a non-significant change in growth at the plot level. Growth increased with regional warming, atmospheric [CO2] and water availability for trees under weak competition, supporting the hypothesis that tree growth of a boreal forest is limited by heat, water and atmospheric CO2, and climate change has positive effect on tree growth. However, for those under strong competition, the tree growth is generally negatively related to climate variables.

The results suggest that upscaling the growth responses of dominant/codominant trees to climate change to a forest or a region can lead to overestimates. Furthermore, the study suggests that increases in carbon sequestration associated with climatic change-enhanced forest growth may be weak in forests where water deficit is not an issue. Finally, the study sheds light on a mechanism of climate change-associated tree mortality. Trees experiencing weak competition grow more rapidly in response to climate change, in turn enhancing their competitiveness and further suppressing the growth of smaller trees that were already experiencing strong competition.

Yong Luo, Lakehead University & University of British Columbia, Canada

Read the full paper online: Climatic change only stimulated growth for trees under weak competition in central boreal forests

Do latex and resin spur diversification? Re-examining a classic example of escape-and-radiate coevolution

July 1, 2019 By gk104 Leave a Comment

Michael Foisy and colleagues contributed a paper to our latest special feature: Macroevolutionary perspectives on biotic interactions. Find out more about their paper below.

A brief history of the project

When an insect chomps on a plant, sometimes the plant tissue will release latex or resin – a “goo” that can be toxic, difficult to digest, and a real nuisance for insect mouthparts. Latex and resin are stored in pressurized canals, which, when damaged, rupture and spill their contents out in dramatic fashion (Figure 1). These canal systems have evolved many times across plants, and play an important role in defence against herbivorous insects.

Rich latex exuded by Papaver somniferum (Papaveraceae), near Chihuahua, Mexico (Photo: Anurag Agrawal).

In 1991, Farrell et al. conducted a now classic study testing whether plants with these pressurized canals are more diverse than closely related plants without canals. Their results were striking: 13 of the 16 comparisons revealed higher species richness when canals were present, supporting the prediction that plant defensive traits are associated with higher diversification rates (i.e. the accumulation of species over time, estimated as the net of speciation minus extinction) in plants.

Their study was one of the first to show strong support for a classic hypothesis about how coevolution between plants and insects could generate biological diversity (Ehrlich & Raven, 1964), and their work remains a prominently cited empirical example even today.

Retesting Farrell et al. 1991

In the three decades since the original study by Farrell et al. (1991), major changes to plant systematic relationships have occurred, and we now have phylogenetic comparative methods that go beyond the sign test they used. In particular, we can explicitly model trait evolution and/or diversification rates. Therefore, our goal was to reassess Farrell’s classic test of whether these defensive “goos” are associated with increased species diversity, but to do so using modern methods and data.

We collected data on the occurrence of latex and resin canals in approximately 300 families and 1000 genera of plants, and used these data (along with updated phylogenetic hypotheses for plant relationships) to test the association between canal evolution and lineage diversification rates. We tested this hypothesis at multiple scales: (i) between clades and (ii) within clades.

As usual, biology is complicated

When we updated and added to the Farrell dataset, interestingly, we no longer found strong support for a relationship between canal evolution and lineage diversification. This was surprising, and so we wanted to zoom in on some of these comparisons, to look at the tempo of diversification in relation to trait evolution.

Within clades, we had enough data to look at two groups: Papaveraceae (poppies) and Araceae (arums). In poppies, the timing of latex evolution coincided with a burst of diversification; however, in Araceae, canal evolution appears to be entirely out of tempo with diversification.

Figure 2 (Read the full paper: https://doi.org/10.1111/1365-2745.13203)

Figure 2 is a simplified version of the figure from our paper. Canal origins are indicated by stars (yellow = latex, green = resin), while shifts in diversification rate are indicated by circles (red = increase, blue = decrease). The relative rates of diversification are shaded in grayscale (darker = higher rates). These data show that diversification coincides with latex evolution in poppies (left), but is uncoordinated with latex and resin evolution in arums (right).

Looking forwards

Thus, it seems that latex and resin canals may not be as consistently replicable drivers of lineage diversification across plants as we previously thought. Future studies could follow up on this work as more data becomes available, for example using more sophisticated models of trait dependent diversification, or taking other factors (such as clade age) into account. We are looking forward to the day that more data are available, so that this association can be even more rigorously examined in even more clades. But in the meantime, latex and resin remain super cool defensive traits with large consequences for plant fitness. Who doesn’t want a powerful goo weapon to fight their enemies?!

Michael Foisy, Loren Albert, Daniel Hughes & Marjorie Weber.

Read the full paper online: Do latex and resin canals spur plant diversification? Re-examining a classic example of escape and radiate coevolution