The Game Objects of Threephase

May 27, 2011

This post is part of a series describing the Threephase project.

The primary geographical units of Threephase are the Country, the State and the City. At any time, there are multiple game worlds running simultaneously. Each game (or Country) has its own unique attributes and available power technologies. The player can choose to either join an existing Country or create a new one (perhaps to experiment with a new regulatory system). A Country's virtual world is ongoing and persistent - players can join and leave at any time.

To join a Country (game and Country are used interchangeably), the player creates a State.

The State is the player's relationship to a certain Country - they can participate in multiple games simultaneously, but with only one State in each game. The player assigns a name, research budget (which effects the cost of new technology) and a map to the new State.

Models

Game/Country

In order to lower the barrier to entry for new players, the player may join and leave games at any time. The time spent finding and joining a game should be minimal. The player should be able to start making in-game decisions as soon as possible to grab and keep their attention. The effects of a State suddenly dropping out of the Country are dampened to not negatively effect the experience for other players when someone leaves the game.

Attributes

A Country has many adjustable attributes that are set at creation. These include, but are not limited to:

  • Minimum & maximum transmission line capacity
  • Relative cost of technology
  • Relative wind speed
  • Type of economic regulation

The attributes affect the difficulty of the game (e.g. relatively higher capital costs make new construction more difficult) similar to how new laws and public policies can affect power utility strategy in real life. They can also simulate different physical environments, e.g. the relative scale of the average wind speed can make a State more or less inclined to add wind turbines to their generator portfolio.

Economic Regulation

Economic regulation is a critical factor in operating a profitable utility. The available economic regulation types in Threephase are rate of return, marginal cost bidding, and locational marginal pricing (discussed in more detail later on). Power utility regulation is an unsolved problem, and the ability to switch between types in Threephase makes comparing scenarios in different regulatory environments a possible use case.

Map

Each State has a map which defines the land and natural resources underneath and neighboring each City. The proximity of City to areas of the map can have a non-trivial effect on the price of certain types of generation in the City because of the abundance of natural resources (discussed further later).

Multiplayer Elements

Threephase is a multiplayer game. Each Country is shared among the players that control a State in that Country. These players currently share national fuel prices. Generators that use non-renewable fuel purchase their operating fuel at prices determined by a national fuel market. Every day, the market price for each fuel type (e.g. coal, oil, natural gas, etc.) is cleared based on the total demand (the sum of the demand of all generators using that fuel, with respect to their projected operating level) and the total supply (the sum of the availability of the fuel's raw natural resource in the State maps).

To bootstrap the economy, each fuel market is initialized with a starting price (randomized within a pre-specified standard deviation, for variety's sake) and a price elasticity of supply. The supply of fuel does not change since State maps are static in the current implementation, so the price elasticity is used to calculate how the fuel price reacts to changes in demand.

The shared fuel prices mean that a player's decision to build many large coal generators can have implications on the generator portfolios of another player ( who may be less inclined to build coal plants due to the increasing cost of fuel).

State

Within a State, the player has complete control over all generators and transmission lines. The player can view the average cost curve of their generators, graphed in order of their average cost. The ideal, cost-minimizing strategy would run the generators in this order - cheapest first.

Average Cost Curve

Average Cost Curve

Threephase makes a conscious decision to use the average cost curve, as opposed to the marginal cost curve, to attempt to take into the account the capital investment of each generator. This is a deviation from the industry norm, done in part to assist my own understanding.

A common point of confusion for non-experts is how utilities could ever expect to do more than depreciate their equipment while operating at the marginal cost. Different types of regulation attempt to compensate in various ways, most commonly with what are known as capacity payments. These are side payments made by the regulator to encourage re-investment and continued expansion of operations.

Geographic Visualization

The dashboard of each state displays a basic visualization of the State and its Citys. The map also visualizes the composition of the land underneath the State. Each small dot is a Block, and each Block has one of a few different types - mountains, plains or water. Each Block also has an index per natural resource, describing its relative abundance in that area. There are currently indices for the non-renewable resources natural gas, coal and oil and for the renewable resources sun, water and wind. In the current implementation, the block types and indices are chosen randomly. This can be improved using map generation algorithms to create more natural and useful land organization - mountain ranges, rivers, etc.

HUD

A screenshot of the State "heads-up display", which shows a map of the natural landscape, where the cities fall in relationship to natural resources, and historical statistics on the price of fuel and electricity.

Location Based Discounts

The location of a City on the map has important implications. Based on the availability of coal within the region, for example, a certain percentage discount is given to coal generators operating in that City. Wind turbines in an area of Blocks with high wind indices will be more effective than in other places.

The discounts are calculated by finding all blocks within a certain radius of the City, scaled based on the population. Larger cities will extend further out from their center point, so they can be expected to utilize a wider area of natural resources.

Map

On the in-game map, the natural resource indices of the land beneath each City can have an effect on the price of local generation. Blocks within a certain radius of a City (green dots within the blue circle, scaled based on population) that contain large amounts of coal or natural gas can make a City a good choice for matching generator types.

Creating Objects

To create a generator, the player selects a GeneratorType from a list of available technologies.

Each Country can customize the list of available GeneratorTypes to simulate different time periods and regulatory environments (e.g. before advanced nuclear or coal with carbon capture and sequestration). The player can compare the available GeneratorTypes based on their attributes to decide which would be the best choice for their portfolio. The current interface is a simple table, sortable by column. Additional comparison visualizations can make the choices easier to understand, and convey some of the issues with new technologies. Lauren Fleishman's work in summarizing and comparing generators is a good inspiration for the user interface.

Generator Type Attributes

The attributes for a GeneratorType loosely belong to three different groups - those that:

  • Scale the marginal cost
  • Scale the capital cost
  • Scale the rate of occasionally positive & negative one-time events

For example, the waste disposal cost effects the marginal cost of power for the GeneratorType. The tax credit lowers the initial capital investment, relative to the size of the generator. The technical reliability effects the frequency of equipment failure, and the technical complexity effects the time it takes to repair a generator once a failure occurs. A complete list is available in the Threephase wiki. Some of the values for attributes were inferred from the U.S. Energy Information Administraton, but others still need to be researched.

Capacity Range

Each GeneratorType also has a range of valid capacities - the number of MWh the GeneratorType can produce at its peak. This range reflects the general capabilities of the GeneratorType, and also its typical applications in real world power grids. For example, gas turbines have relatively lower capacity limits than nuclear generators, and they are typically used as peaking plants (to cover spikes in demand) as opposed to baseload plants which are more efficient in large capacities.

Object Type Extensibility

These attributes and effects are not specific to generators. The objects in Threephase are members of a TechnicalComponent hierarchy, allowing them to share the flexibility enjoyed by generators. Transmission lines, power storage devices, and other component classes all have these attributes.

Technical Components

Generators, transmission lines and power storage devices all inherit from a common parent type - the TechnicalComponent. This allows the game to share code when interacting with each type of object, and still allow for some customization.

In the case of transmission lines, the player can choose from LineTypes such as high-voltage DC and high-voltage AC of varying capacities and resistances.

Most of the attributes are shared with generators through the TechnicalComponent model, but class-specific attributes (e.g. underground v.s. above ground lines) are also supported.

Implementation Note

The relationships are maintained using single-table inheritance (so GeneratorType, LineType and StorageDeviceType share a database table) and polymorphic associations (so a State can reference instances of the three classes in a generic fashion).

Continue to the next section on game mechanics.

Other Threephase Articles